Five-membered Cyclic Anhydride Research Articles

High-performance epoxy covalent adaptable networks enabled by alicyclic anhydride monoesters

Transesterification-based covalent adaptable networks (CANs) exhibit malleability and reprocessability, yet are highly dependent on the addition of a large amount of catalysts to accelerate transesterification reactions. A strategy of dynamic transfer auto-catalysis has been proposed by pending dynamically transferable anhydride monoesters at the network, which will greatly enhance the auto-catalytic efficiency. Here two trifunctional acids from alicyclic five-membered cyclic anhydride and six-membered cyclic anhydride, were synthesized and cured with bisphenol A epoxy monomer, respectively. The reprocessability, degradability and mechanical properties of the obtained epoxy CANs can be readily tuned by changing the structure of the trifunctional acid. The conformational transition of the non-planar ring accelerated network rearrangement and the large steric hindrance slowed down the degradation rate and the rigid feature endowed high thermal and mechanical properties of the epoxy CANs. In addition, the kinetically slow formation of six-membered cyclic anhydride than that of five-membered cyclic anhydride, led to the lower dynamic transfer auto-catalytic efficiency of its monoester. However, its good solubility in water gave it a fast degradation rate.

High temperature ATR-FTIR characterization of the interaction of polycarboxylic acids and organotrialkoxysilanes with cellulosic material.

To convey novel properties to textile surface cotton-based fabrics were impregnated with solutions containing various chemical agents, such as butane-1,2,3,4-tetracarboxylic acid or hydrolyzed organotrialkoxysilanes (3-amino)propyltriethoxysilane), (3-glycidylpropyl)-trimethoxysilane, (3-triethoxysilylpropyl)succinic acid anhydride, octyltriethoxysilane, and Dynasylan F8815 (fluoroalkylfunctional water-borne oligosiloxane). The as-prepared cotton specimens were dried and cured at elevated temperatures. As the curing process can be performed at different temperatures, the impregnated and dried cotton samples were studied by means of time-dependent ATR-FTIR spectroscopy in an attempt to get a closer insight into the process mechanism. The results make evident that the butane-1,2,3,4-tetracarboxylic acid and (3-triethoxysilylpropyl)succinic acid anhydride reacts with the hydroxyl groups of the cellulose via a five-membered cyclic anhydride intermediate which is confirmed by vibration bands appearing at 1782cm-1 (symmetric stretching vibration of the anhydride carbonyl group) and at 1861cm-1 (antisymmetric stretching vibration of the anhydride carbonyl group).

Anti-inflammatory and α-Glucosidase Inhibitory Activities of Labdane and Norlabdane Diterpenoids from the Rhizomes of Amomum villosum.

A new tetranorditerpenoid (1), two new labdane diterpenoids (2, 3), and nine known analogues (4-12) were isolated from the rhizomes of Amomum villosum var. xanthioides. Compound 1 is an unprecedented rearranged tetranorlabdane diterpenoid, featuring a 6/6/5 fused tricarbocyclic skeleton with an α,β-unsaturated cyclopentenone unit, while 2 is a structurally rare labdane diterpenoid carrying a five-membered cyclic anhydride moiety. Their structures and absolute configurations were established on the basis of spectroscopic data and the experimental and calculated ECD data. Compound 4 showed inhibitory activity against nitric oxide production, with an IC50 value of 2.4 μM, and also inhibited α-glucosidase activity (IC50 = 10.0 μM).

Synthesis and biomedical applications of functional poly(α-hydroxy acids) via ring-opening polymerization of O-carboxyanhydrides.

Poly(α-hydroxy acids) (PAHAs) are a class of biodegradable and biocompatible polymers that are widely used in numerous applications. One drawback of these conventional polymers, however, is their lack of side-chain functionalities, which makes it difficult to conjugate active moieties to PAHA or to fine-tune the physical and chemical properties of PAHA-derived materials through side-chain modifications. Thus, extensive efforts have been devoted to the development of methodology that allows facile preparation of PAHAs with controlled molecular weights and a variety of functionalities for widespread utilities. However, it is highly challenging to introduce functional groups into conventional PAHAs derived from ring-opening polymerization (ROP) of lactides and glycolides to yield functional PAHAs with favorable properties, such as tunable hydrophilicity/hydrophobicity, facile postpolymerization modification, and well-defined physicochemical properties. Amino acids are excellent resources for functional polymers because of their low cost, availability, and structural as well as stereochemical diversity. Nevertheless, the synthesis of functional PAHAs using amino acids as building blocks has been rarely reported because of the difficulty of preparing large-scale monomers and poor yields during the synthesis. The synthesis of functionalized PAHAs from O-carboxyanhydrides (OCAs), a class of five-membered cyclic anhydrides derived from amino acids, has proven to be one of the most promising strategies and has thus attracted tremendous interest recently. In this Account, we highlight the recent progress in our group on the synthesis of functional PAHAs via ROP of OCAs and their self-assembly and biomedical applications. New synthetic methodologies that allow the facile preparation of PAHAs with controlled molecular weights and various functionalities through ROP of OCAs are reviewed and evaluated. The in vivo stability, side-chain functionalities, and/or trigger responsiveness of several functional PAHAs are evaluated. Their biomedical applications in drug and gene delivery are also discussed. The ready availability of starting materials from renewable resources and the facile postmodification strategies such as azide-alkyne cycloaddition and the thiol-yne "click" reaction have enabled the production of a multitude of PAHAs with controlled molecular weights, narrow polydispersity, high terminal group fidelities, and structural diversities that are amenable for self-assembly and bioapplications. We anticipate that this new generation of PAHAs and their self-assembled nanosystems as biomaterials will open up exciting new opportunities and have widespread utilities for biological applications.

Electrospun Ultrathin Poly(vinyl alcohol) Fibre Assemblies Modified by Means of Polycarboxylic Acid / Sodium Hypophosphite

A viscous solution consisting of poly(vinyl alcohol) (PVA), butane-1,2,3,4-tetracarboxylic acid (BTCA) and sodium hypophosphite monohydrate (SHP) has been prepared and subjected to an electrospinning process in an attempt to produce BTCA-crosslinked ultrathin PVA fibre mats. At elevated temperatures the carboxyl groups of BTCA react with the hydroxyl groups of PVA via a five-membered cyclic anhydride thus forming ester linkages. The measurement of the fibre diameters of the electrospun fibres created at various high voltages (10, 15, and 20 kV) revealed that the diameters of the fibres were in the range of 0.98 - 1.20 μm. Single layer and double layer fibre assemblies were prepared and thermally treated at 180 °C. The as-prepared ultrathin PVA fibre assemblies were analyzed by means of scanning electron microscopy (SEM), indicating that the morphology of the fibres had been changed. Fourier transform infrared/attenuated total reflection spectroscopy (FT-IR/ATR), X-ray powder diffraction (XRPD) and physical properties, such as water vapour absorption (WVA), water vapour transmission (WVT) and tensile strength were evaluated. The incorporation of BTCA resulted in an increase of WVA and a decrease of WVT. The tensile strengths of the cured PVA mats were remarkably decreased, when BTCA/SHP had been added.

Cross-Linking Cotton Cellulose by the Combination of Maleic Acid and Sodium Hypophosphite. 1. Fabric Wrinkle Resistance

Durable press finishing agents used to produce wrinkle-resistant cotton garments are cross-linking agents for cotton cellulose. Polycarboxylic acids have been the promising durable press finishing agents to replace the formaldehyde-based reagents when sodium hypophosphite (NaH2PO2) was used as the catalyst. In our previous research, we found that a polycarboxylic acid esterifies cotton cellulose by first forming a five-membered cyclic anhydride as a reactive intermediate. Maleic acid (MA) is a bifunctional carboxylic acid, therefore is not able to form the second cyclic anhydride intermediate once it forms the first ester linkage with cotton. However, we discovered that MA imparted wrinkle resistance to cotton fabrics when NaH2PO2 was present, thus indicating that MA was able to cross-link cotton. Sodium hypophosphite functions as the catalyst for the esterification of cellulose by MA, and the esterification takes place at relatively low temperatures (≥130 °C). Esterification of MA forms single esterlinka...

Structural characterization of Langmuir–Blodgett films of 4,5-bis(dodecyloxy)phthalic acid

In this work, the formation of Langmuir monolayer of 4,5-bis(dodecyloxy)phthalic acid (DPA) molecule at the air–water interface, surface-pressure area ( π– A) isotherm and stability of this monolayer was investigated. The structural characterization of Langmuir–Blodgett (LB) films of DPA deposited on aluminium covered glass substrate was studied using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) measurements. For FTIR measurements, p-polarized grazing angle (GAIR) and horizontal attenuated total reflectance (HATR) techniques have been employed to characterize the LB films. The molecular structure of LB films was investigated by comparing the GAIR and HTAR spectra. The two extra bands that appeared in the FTIR spectra of LB films suggest that the carbonyl groups are bonded to the adjacent carbons of head groups and the carboxylic acids of head groups are capable of forming five-membered cyclic anhydrides in all LB films. The slightly downward shifts of the ν(CH 2) stretching bands are indicative of the increase in conformational order from gauche conformers to highly ordered transconformers in the hydrocarbon chain with increasing number of layers. Changes in intensity between the p-polarized GAIR and HATR spectra may indicate that the alkyl chains are almost perpendicular to the substrate in LB films. The singlet absorption due to the δ(CH 2) and ρ r(CH 2) modes indicated that in LB films of DPA alkyl chains are packed in hexagonal structure. The XRD results show that all the multilayer structure is Y-type and the alkyl chains aligned almost vertically in the LB films.

Crosslinking of rayon fibers with co-oligomer of maleic acid and methylacrylate and their responses to water

A co-oligomer of maleic acid and methylacrylate (COMM) was used to crosslink rayon fibers. It was shown to be a more effective polycarboxylic crosslinking agent than 1,2,3,4-butanetetracarboxylic acid (BTCA) as judged by the enhancement of mechanical properties. Similar to BTCA, COMM formed a five-membered cyclic anhydride intermediate by anhydridisation of a carboxyl group pair, and subsequently the anhydride intermediate reacted with cellulose in the amorphous regions to form an ester linkage. Apparent crosslinking degree (ACD) of the crosslinked rayon fibers was proposed to quantify the crosslinking efficiency of COMM. The water sorption isotherm was not strongly affected by crosslinking whereas water retention after swelling in excess water decreased with the degree of crosslinking.

Identification and quantification of cotton-bound, cyclic polycarboxylic acids by means of isocratic HPLC.

Cotton fabrics are modified by means of polycarboxylic acids (PCA) in combination with an inorganic catalyst in order to impart durable press properties. To evaluate the effectiveness of cyclic PCA, 100% cotton fabrics were treated with 1,2,3,4,5,6-cyclohexanehexacarboxylic acid (CH-HCA), 1,3,5-cyclohexanetricarboxylic acid (CH-TCA), 1,2,3,4-cyclopentanetetracarboxylic acid (CP-TCA), and 1,2,3,4-tetrahydrofurantetracarboxylic acid (THF-TCA) in combination with sodium hypophosphite (SHP) as catalyst. The amount of PCA that reacted with the cellulosic material was determined by means of isocratic HPLC (Aminex HPX-87-H). The results clearly indicate that the cyclic PCA are less effective in respect of durable press performance. CH-TCA does not react with the cellulosic material thus confirming the assumption that the crosslinking reaction between PCA and the cellulose proceeds via a five-membered cyclic anhydride.

IR spectroscopy study of cyclic anhydride as intermediate for ester crosslinking of cotton cellulose by polycarboxylic acids. V. Comparison of 1,2,4‐butanetricarboxylic acid and 1,2,3‐propanetricarboxylic acid

AbstractIn recent years extensive efforts have been made to use multifunctional carboxylic acids as formaldehyde‐free crosslinking agents for cotton to replace the traditional formaldehyde‐based N‐methylol reagents. In our previous research we found that a polycarboxylic acid esterifies cellulose through the formation of a five‐membered cyclic anhydride intermediate by dehydration of two adjacent carboxyl groups. In this research we used Fourier transform IR (FTIR) spectroscopy to study the formation of cyclic anhydride intermediates and crosslinking of cotton by 1,2,4‐butanetricarboxylic acid (BTA) and 1,2,3‐propanetricarboxylic acid (PCA). BTA and PCA form five‐membered cyclic anhydrides in the same temperature range. Both acids form the anhydrides at lower temperatures when a catalyst is present. When an acid molecule is bonded to cotton through an ester linkage, only PCA is able to form a second anhydride intermediate. We found that PCA is a more effective crosslinking agent, and it imparts higher levels of wrinkle resistance to the cotton fabric than BTA. Therefore, the formation of a five‐membered cyclic anhydride by a polycarboxylic acid accelerates the esterification of cotton by the acid. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2142–2150, 2001

FTIR Spectroscopy Study of Ester Crosslinking of Cotton Cellulose Catalyzed by Sodium Hypophosphite

In previous research, we found that sodium hypophosphite (NaH2PO2) reduces the temperature required for the formation of anhydride intermediates by polycarboxylic acids. We also found that a chemical reaction between the anhydride intermediate of 1,2,3,4-butanetetracarboxylic acid (BTCA) and NaH2PO2 takes place when the temperature rises above 200°C. In this research, we use Fourier transform infrared (FTIR) spectroscopy and thermal analysis to confirm that NaH2PO2 reacts with cis-1,2-cyclohexanedicarboxylic anhydride (CHDN) at temperatures above 170°C. NaH2PO2 catalyzes the formation of the cyclic anhydride intermediate by 3-butene-1,2,3-tricarboxylic acid (BTTA) on cotton. In the presence of NaH2PO2, BTTA forms a five-membered cyclic anhydride on cotton at temperatures as low as 120°C. However, no esterification takes place on the fabric at such temperatures. The data also indicate that NaH2PO2 reacts with the anhydride intermediate when the temperature rises above 180°C. We have found that esterification of cotton cellulose by BTTA takes place only when NaH2PO2 is present and the temperature is above 180°C. Therefore, the catalysis effects of NaH2PO2 for cotton esterification by BTTA are probably related to the reaction between NaH2PO2 and the anhydride intermediate.

FT-IR and FT-raman spectroscopy study of the cyclic anhydride intermediates for the esterification of cellulose: III. Cyclic anhydrides formed by the isomers of cyclohexanedicarboxylic acid

Multifunctional carboxylic acids have been used as crosslinking agents for cotton and wood pulp cellulose. In our previous research, we found that a polycarboxylic acid esterifies cellulose through the formation of a 5-membered cyclic anhydride intermediate by the dehydration of two carboxyl groups. In this research, we studied the formation of cyclic anhydride intermediates by different isomers of cyclohexanedicarboxylic acid (CHA) so that we can elucidate the effects of molecular structure on the formation of the anhydride intermediates. We found that both cis-and trans-1,2-CHA form 5-membered anhydride intermediates when temperature reaches their melting points and that cis-1,2-CHA forms the cyclic anhydride at temperatures lower than does trans-1,2-CHA. 1,3-CHA forms 6-membered cyclic anhydride at temperatures much higher than its melting point. The formation of a 5-membered cyclic anhydride intermediates takes place at temperatures lower than that of a 6-membered anhydride. This is probably the main reason why those polycarboxylic acids with their carboxylic acid groups bonded to the adjacent carbons of the molecular backbones are more effective crosslinking agents for cellulose than those with their carboxylic groups bonded to the alternative carbons. No formation of cyclic anhydride was found for 1,4-CHA. The formation of a five-membered cyclic anhydride was accelerated by monosodium phosphate, which is used as a catalyst for the esterification of cotton cellulose by polycarboxylic acids.

FTIR Spectroscopy Study of the Formation of Cyclic Anhydride Intermediates of Polycarboxylic Acids Catalyzed by Sodium Hypophosphite

In recent years, extensive efforts have been made to find formaldehyde-free durable press finishes to replace the traditional formaldehyde-based N-methylol compounds. 1,2,3,4-Butane-tetracarboxylic acid (BTCA) has been the most efficient nonformaldehyde crosslinking agent for cotton, with sodium hypophosphite (NaH2PO2) being the most effective catalyst. In our previous research, we found that a polycarboxylic acid esterifies cellulose through the formation of a five-membered cyclic anhydride intermediate by the dehydration of two adjacent carboxyl groups. In this research, we use Fourier transform infrared spectroscopy (FTIR) to study the formation of cyclic anhydride intermediates by BTCA and poly(maleic acid) (PMA) with and without the presence of NaH2PO2. In the absence of NaH2PO2, BTCA forms the cyclic anhydride only when the temperature reaches the vicinity of its melting point. In the presence of NaH2PO2, however, the anhydride forms at much lower temperatures. We have found that NaH2PO2 weakens the hydrogen bonding between the carboxylic acid groups of BTCA, contributing to accelerated anhy dride formation at lower temperatures. Sodium hypophosphite also accelerates the for mation of the anhydride intermediates by polycarboxylic acids in an amorphous state. The FTIR spectroscopy data show that there is a chemical reaction between the anhydride intermediate and NaH2PO2 when the temperature climbs above 200°C.

Infrared spectroscopy studies of cyclic anhydrides as intermediates for ester crosslinking of cotton cellulose by polycarboxylic acids. IV.In situ free radical copolymerization of maleic acid and itaconic acid on cotton

Polycarboxylic acids have been used as crosslinking agents for cotton fabrics and paper to replace the traditional formaldehyde-based reagents. Previously, we found that a polycarboxylic acid esterifies cotton cellulose through the formation of a five-membered cyclic anhydride intermediate. Both maleic acid (MA) and itaconic acid (ITA) are extremely difficult to polymerize under conditions normally used for free radical polymerization. It has been reported in the literature that treatment of cotton fabric with a mixture of MA and ITA significantly improved wrinkle-resistance of the fabric. In this research, we investigated the in situ copolymerization of MA and ITA on cotton fabric. Fourier transform-infrared spectroscopy was used to study the anhydride carbonyl formed on the cotton fabric treated with the mixtures of MA and ITA. A redox titration technique also was applied to determine the quantity of alkene double bonds on the treated fabric. It was found that free radical copolymerization of MA and ITA does not occur on the fabric at elevated temperatures when potassium persulfate is present as an initiator. It does occur, however, when both potassium persulfate and sodium hypophosphite are present on the fabric. The in situ copolymerization on the cotton fabric probably is initiated by a reduction–oxidation system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 327–336, 2000

Ft-Ir and Ft-Raman Spectroscopy Study of the Cyclic Anhydride Intermediates for the Esterification of Cellulose: Ii. Formation of Anhydrides Catalyzed By Sodium Hypophosphite

A five-membered cyclic anhydride is the reactive intermediate of polycarboxylic acids for esterifying cellulose. In our previous research, we found that polycarboxylic acids in a crystalline state start to form 5-membered cyclic carboxylic anhydrides when the temperature reaches the vicinity of their melting points, and that hydrogen bonding between carboxylic acid groups prevents the formation of the cyclic anhydride intermediates at lower temperatures. In this research, we studied the formation of cyclic anhydride intermediates by 1,2,3,4-butane-tetracarboxylic acid (BTCA) and itaconic acid (IA) in the presence of sodium hypophosphite (NaH 2 PO 2 ) ' We found that NaH 2 PO 2 weakens the hydrogen bonding between the carboxylic acid groups of BTCA. In the presence of NaH 2 PO 2 , BTCA forms the cyclic anhydride at temperatures significantly lower than its melting point. NaH 2 PO 2 also reduces the temperatures required for the formation of the anhydride intermediate of IA on cotton fabric. The catalysis for the formation of anhydride intermediates by NaH 2 PO 2 contributes to the acceleration of esterification of cotton cellulose by polycarboxylic acids.

Formation of five-membered cyclic anhydride intermediates by polycarboxylic acids: Thermal analysis and Fourier transform infrared spectroscopy

Butanetetracarboxylic acid (BTCA) has been used as the most effective nonformaldehyde crosslinking agent for cotton and wood pulp cellulose. Our previous research has indicated that a polycarboxylic acid esterifies cellulose in two steps: the formation of a five-membered cyclic anhydride intermediate by the dehydration of two adjacent carboxyl groups, and the reaction between cellulose and the anhydride intermediate to form an ester linkage. In this research, we investigated the formation of carboxylic anhydrides by BTCA and other polycarboxylic acids in powder forms, and as finishes applied to cotton fabric using thermal gravimetry, differential scanning calorimetry, and Fourier transform infrared spectroscopy. We found that BTCA and other polycarboxylic acids in powder forms start to form five-membered cyclic carboxylic anhydrides when the temperature reaches the vicinity of their melting points. The formation of carboxylic anhydride is accelerated above the melting points. We also found that BTCA forms anhydrides at lower temperatures when it is applied to cotton fabric as a finish. An increase in temperature increases both the amount of anhydride and the amount of ester formed on the cotton fabric. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2711–2718, 1998

Infrared spectroscopy studies of the cyclic anhydride as the intermediate for the ester crosslinking of cotton cellulose by polycarboxylic acids. III. Molecular weight of a crosslinking agent

Polycarboxylic acids have been used as nonformaldehyde crosslinking agents for cotton fabrics to replace the traditional N-methylol reagents. In this research, we compared 1,2,3,4-butanetetracarboxylic acid (BTCA) with poly(maleic acid) (PMA) as crosslinking agents for cotton cellulose. BTCA and PMA have similar molecular structures with carboxyl groups bonded to their molecular backbones, and both form five-membered cyclic anhydride intermediates during a curing process. However, BTCA is a more effective crosslinking agent for cotton cellulose than PMA. This is mainly attributed to the differences in the mobility of the anhydride intermediates to access the cellulosic hydroxyl groups during a curing process. The mobility of the anhydride intermediate of PMA is reduced due to its molecular size and multiple bonding between a PMA molecule and cellulose. Consequently, more anhydride and less ester are detected on the cotton fabric treated with PMA than on the fabric treated with BTCA. The amount of the unreacted anhydride intermediate on the fabric treated with PMA is reduced whereas the amount of ester is increased when another hydroxyl-containing compound of low molecular weight is present. Thus, the infrared spectroscopy data show a clear link between the molecular weight of a polycarboxylic acid and its effectiveness for crosslinking cotton cellulose. © 1997 John Wiley & Sons, Inc.

Infrared spectroscopy studies of the cyclic anhydride as the intermediate for the ester crosslinking of cotton cellulose by polycarboxylic acids. II. Comparison of different polycarboxylic acids

Polycarboxylic acids have been used as crosslinking agents for cotton cellulose. In our previous research, we used Fourier transform infrared (FT-IR) spectroscopy to investigate the formation of five-membered cyclic anhydride intermediates on cotton fabric by different polycarboxylic acids. In this research, we found that those polycarboxylic acids capable of forming both five- and six-membered cyclic anhydrides form only five-membered cyclic anhydrides. We compared the effectiveness of the polycarboxylic acids with different molecular structures for esterifying cellulose. Those polycarboxylic acids, which have their carboxyl groups bonded to the adjacent carbons of their molecular backbones and are capable of forming five-membered cyclic anhydrides, are more effective for esterifying cellulose than those polycarboxylic acids having their carboxyl groups bonded to the alternative carbons. The only six-membered cyclic anhydride identified is the anhydride formed on the cotton fabric treated with poly(acrylic acid). © 1996 John Wiley & Sons, Inc.

FT-IR Spectroscopy Study of the Polycarboxylic Acids Used for Paper Wet Strength Improvement

Polycarboxylic acids have been used as cross-linking agents for cellulose to increase the wet strength of paper. In this research, we applied Fourier transform infrared (FT-IR) spectroscopy to study the kraft paper treated with poly(maleic acid) and 1,2,3,4-butanetetracarboxylic acid. FT-IR spectroscopy is used to measure the carboxyl of a polycarboxylic acid and ester on the treated paper. The ester carbonyl band intensity and the carbonyl band intensity ratio (ester/carboxylate) are used for the evaluation of the effectiveness of a polycarboxylic acid for cross-linking cellulose on the paper. The correlation between the ester carbonyl band intensity and the wet strength improvement of the treated paper reveals that the increase in the paper wet strength by a polycarboxylic acid is the result of ester cross-linking of cellulosic fibers and molecules. We identified a five-membered cyclic anhydride intermediate formed on the paper during the curing processes. The infrared spectroscopy data support the reac...

THE EFFECT OF LOCATING THE SULFONYL GROUP IN A FIVE-MEMBERED RING ON THE BALANCE OF ELIMINATION VS. SUBSTITUTION REACTIONS OF SULFONIC ACID DERIVATIVES

Abstract The simplest examples of both a five-membered cyclic sulfonic anhydride (ethane-1, 2-disulfonic anhydride, 3) and a sulfonylammonium salt (2, 2-dimethylisothiazolidinium 1, 1-dioxide fluorosulfate, 13), are found to react with triethylamine and an alcohol via direct displacement at sulfur and not by way of the sulfene. When taken with previous observations these results lead to the conclusion that five-membered cyclic sulfonic acid derivatives can generally be expected to react entirely by direct displacement, even in those reactions in which the acylic or six-membered cyclic analogues react entirely via the sulfene.