Spiro Ethers Research Articles

1,5,7-Triazabicylodec-5-ene-Promoted Direct Vinylogous Aldol Reaction for the Synthesis of 3-Hydroxy-2-oxoindole Derivatives

A simple and efficient method has been developed for the synthesis of 3-hydroxy-2-oxoindole derivatives through a direct vinylogous aldol reaction of allylic esters with isatins, catalyzed by 1,5,7-triazabicyclodec-5-ene. This method affords a variety of 3-hydroxy-2-oxoindole derivatives in moderate to excellent yields with high regioselectivities. An asymmetric version of this reaction catalyzed by Corey’s chiral guanidine proceeded with moderate enantioselectivity. The protocol can also be used to synthesize isatin spiro ethers.

Ring-closing metathesis as a tool for the efficient preparation of chiral spirocyclic ethers from homoallylic alcohols

The preparation of chiral spirocyclic ethers via allylic etherification/olefin metathesis of homoallylic alcohols is investigated. This reaction sequence transforms the enantiopure substrate alcohols, synthesized by a one-pot asymmetric rhodium-catalyzed conjugate addition/metal-mediated allylation procedure, into the desired spiro ethers with full conversions and in excellent isolated yields. The synthetic sequence provides an efficient means for a rapid construction of functionalized spiro ethers in a stereoselective manner.

Iodine-Catalyzed Synthesis of Five-Membered Cyclic Ethers from 1,3-Diols under Solvent-Free Conditions

Intramolecular etherification of 1,3-diols was investigated using iodine as a catalyst under solvent-free conditions. The reaction proceeded to completion in a heterogeneous system. Five-membered cyclic ethers were obtained by intramolecular cyclization of 1,3-diols with dehydration. A propella ether (11-oxatricyclo[4.4.3.0(1,6)]tridecane) was conveniently synthesized from a 1,3-diol (6-(2-hydroxyethyl)spiro[4.5]decan-6-ol) in 86% yield with carbon skeleton rearrangement under the following conditions: a temperature of 60 degrees C, a molar ratio of 1,3-diol:iodine = 1:0.2, and a time period of 3 h. Bicyclic ethers were also obtained from the corresponding 1,3-diols, but spiro ethers were obtained in lower yield. Terpenic cyclic ethers were efficiently synthesized from the corresponding 1,3-diols, derived from (+)-camphor and (-)-fenchone. In the case of etherification with a mechanism of carbon skeleton rearrangement, the yield of the solvent-free reaction was as high as that of the corresponding reaction in solution. Etherification reactions with carbon skeleton rearrangement proceeded more smoothly than those with hydride shift.

X-ray Crystallographic and Mass Spectrometric Probing of the Conformational and Ionophoric Properties of Stereoisomeric Hexatetrahydrofuranylhexane Segments

A full account of the synthesis of the 12 hexacyclic tetrahydrofuran isomers represented by the nearby formulas is first provided. The key steps involved in further elaboration of the spiro ethers 12, 15, 28, and 45 include controlled ozonolysis, 1,2-addition of the Normant reagent, and heterocyclization. Eight of the end products proved to be sufficiently crystalline to enable X-ray analysis and determination of their solid-state conformational features. The alkali metal ion selectivities of the 12 hexamers were evaluated by a picrate extraction method and by electrospray ionization mass spectrometry (ESI-MS) which indicated that small, but significant, selectivity differences exist within the groups of diastereomers. These results revealed that each hexamer demonstrated a preference for lithium ion complexation relative to sodium or potassium ion complexation. Stereoisomeric classification of the hexamers was based on the competition between two dissociation routes promoted by collision-induced dissociation. The preference for each of the two dissociation pathways, both of which involved cleavage at the midpoint of the hexamer, correlated with the stereochemical configurations (syn versus anti) of the THF groups near the termini.

A Facile Approach to the Synthesis of Allylic Spiro Ethers and Lactones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Metathetic approach towards macrocyclic bis‐ethers and in sequence use of barbier reaction and RCM for spirocyclic ethers

Abstractmagnified imageAn efficient method for the synthesis of novel macrocyclic bis‐ethers from alizarin and also some new spiro ethers from various substituted ketones by the use of Barbier and ring‐closing metathesis (RCM) reactions has been developed.

A Facile Approach to the Synthesis of Allylic Spiro Ethers and Lactones

Treatment of 3-[(alkoxycarbonyl)alkyl]-substituted conjugated cycloalkenones with diisobutylaluminum hydride at -78 °C followed by acid quenching furnishes spiro ethers, whereas the corresponding 3-(carboxyalkyl)-substituted cycloalkenones generate spiro lactones upon reaction with sodium borohydride at 30 °C followed by acid quenching.

Exploring structural effects of ketone catalysts on asymmetric epoxidation of olefins

Several ketone catalysts containing spiro ethers and lactones have been investigated for the asymmetric epoxidation of olefins. The results showed that substituents on the spiro ring of the ketone catalysts have profound effects on enantioselectivity. Results also suggested that the high enantioselectivities previously observed for conjugated cis-olefins with oxazolidinone containing ketones could be partially due to attractive interactions between the R π group of the olefin and the carbonyl group of the oxazolidinone. In addition, nonbonding interactions such as van der Waals forces and/or hydrophobic interactions between the olefin substituents and the nitrogen substituents of the oxazolidinone may also be involved in stereodifferentiation. The information gained provides additional understanding of factors important for ketone catalyzed epoxidations.

ChemInform Abstract: Synthesis of Spiro Ethers by Ring Closing Metathesis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of Spiro Ethers by Ring Closing Metathesis

Synthesis of Spiro Ethers by Ring Closing Metathesis

Enantioselective Synthesis of Spiro Ethers and Spiro Ketals via Photoaddition of Dihydro-4-pyrones to Chiral 1,3-Dioxin-4-ones

A versatile and highly stereoselective synthesis of spiro ethers and spiro ketals is presented. The key step in the developed synthetic sequence is based on diastereoselective intramolecular photoaddition of dihydro-4-pyrones to chiral 1,3-dioxin-4-ones. Subsequent fragmentation of the produced four-membered ring provides spiro ether structures. The spiro ethers can be transformed to their corresponding spiro ketals, with retention of configuration at the spiro center, via Baeyer−Villager oxidation. The configuration of the spiro center is defined by the facial selectivity at the photocycloaddition step. Two examples of complete stereofacial selectivity were achieved. The unique and important application of the developed sequence was demonstrated in enantioselective synthesis of a less thermodynamically stable spiro ketal 43.

Concise Synthesis of cis- and trans-Theaspirones via Oxonium Ion-Initiated Pinacol Ring Expansion

The odoriferous principle of black tea has been produced from 2,2-dimethylcyclopentanone. The reaction sequence begins with 1,2-addition of 5-lithio-2-methyl-2,3-dihydrofuran to this ketone and immediate acid-catalyzed ring expansion of the resulting carbinols to a separable pair of spiro ethers. Individual conversion of these diastereomers to α,β-unsaturated ketones is followed by tandem condensation with the methyllithium−lithium bromide complex and oxidation with pyridinium chlorochromate.

Structure‐Odor Correlation XVII. Synthesis and Olfactory Properties of further Theaspirane Analogs

AbstractAlkylation of ethyl geranate (5) with the bromo esters 7 and 8 gave the β,γ‐unsaturated esters 10 and 11, which could be isomerized to 13 and 14 by treatment with DBU. The α,β‐unsaturated esters 12–14 were cyclized to 15–17, and subsequent reduction of 15–17 led to the diols 18–20. Final cyclization afforded the spiro ethers 2–4. – The olfactive properties (intensity and quality) of the theaspirane analogs 1–4 are determined by the conformational flexibility of the respective molecule. Thus, the rigid 1 and 2 have strong camphoraceous odors. Augmenting flexibility (→3, →4) results in weaker, fruity‐woody notes.

The intramolecular silyl-modified Sakurai (ISMS) reaction. A simple and versatile synthesis of tetrahydropyrans, spiro ethers, and spiro ketals

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe intramolecular silyl-modified Sakurai (ISMS) reaction. A simple and versatile synthesis of tetrahydropyrans, spiro ethers, and spiro ketalsIstvan E. Marko, Abdelaziz Mekhalfia, Daniel J. Bayston, and Harry AdamsCite this: J. Org. Chem. 1992, 57, 8, 2211–2213Publication Date (Print):April 1, 1992Publication History Published online1 May 2002Published inissue 1 April 1992https://doi.org/10.1021/jo00034a003RIGHTS & PERMISSIONSArticle Views718Altmetric-Citations57LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (397 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Structure‐odour correlation, part XV1: Macrocyclic spiro ethers

AbstractFrom cyclooctanone (1) and cyclododecanone (2) the spiro ethers 18–23 were prepared via the yne‐diols 6–11 and the ene‐diols 12–17. Hydrogenation of 21–23 leads to the spiro tetrahydrofurans 24–26.Olfactive evaluation showed that the odour of 18 (camphor, fresh, green) is very similar to that of the unsubstituted analogue B (R1, R2 = H). This can be explained by a similar steric situation of the osmophoric dihydrofuran ring in both these compounds. Increasing substitution at C‐2 (18 → 19 → 20) diminishes the camphoraceous sensation stepwise with increasing herbaceous notes. The macrocyclic spiro ethers 21–23 exhibit interesting woody fragrances with different undertones. Particularly, 22 is most pleasant with some powdery, balsamic and musk notes. The saturated spiro ethers 24–26 smell similar but very weak.

Structure-odour correlation, part XII1: Dehydrotheaspirane analogues

From isophorone (1) and camphor (2) the spiro ethers 3–8 were prepared via the yne-diols 12–17 and the ene-diols 18–23. The attempted ring closure of 21 and 22 with KHSO4 furnished only the carbonyl compounds 24 and 25. Under these conditions 23 gave a mixture of the isomers 8a and 8b. Olfactive evaluation showed that the odour goes stepwise with increasing substitution at C-2 (3 4 5) or C-5′ (6 7 8) from harsh, camphoraceous to fruity and finally nutty, woody notes. These sensations are comparable with those of the dehydrotheaspiranes (type B) showing that the methyl groups in a position to the osmophoric oxygen atom are particularly important for the odour profile. The strongly hindered interaction of the ether atom of 8a with the receptor in comparison to the situation of the isomer 8b effects a great difference in both odour quality and quantity of these isomers.

ChemInform Abstract: Total Synthesis of (+)‐Breynolide.

AbstractEach of the spiro ethers (XIII) and (XIV) can be converted to the natural product via a five‐step sequence.

Conformational analysis of 1-oxaspiro[5.5]undecanes. A powerful probe for the endo and the exo anomeric effects in acetals

A 13C nuclear magnetic resonance spectroscopy study of 1-oxaspiro[5.5]undecanes 1, 4, and 5 as a function of temperature is reported. Compound 1 exists as a rapidly equilibrating mixture of a major and a minor conformer (1a and 1b) at room temperature that can be observed at low temperature. By comparison, 1,7-dioxaspiro[5.5]undecane 2 is conformationally rigid in a single conformation (2a) at room temperature. This completely different behavior demonstrates the importance of the endo and the exo anomeric effects in the acetal function. Keywords: spiro ethers, conformational analysis, 13C NMR.

Terpenes and terpene derivatives - XV. [1 ] Synthesis of 4,8-dimethyl-2-(2-methyl-1-propenyl)--1-oxaspiro(4.5]dec-7-ene (“bisabolene oxide”)

Starting from the ketones 3 and 4 the synthesis of six spiro ethers with an l-oxaspiro[4.5]decane skeleton is described. Five of them, 9a , b , 10a , 19 and 19 represent typical partial structures of the sesquiterpenoid spiro ether 1 . The unambiguous synthesis of 1 shows a previous assignment of “'bisabolene oxide“' to structure 1 to be wrong.

Synthetic studies toward marine toxic polyethers (1) a stereocontrolled synthesis of the C-segnent of okadaic acid

Okadaic acid was antithesized into three segments A, B and C, and this paper deals with the synthesis of the C-segment in the form of 24, which was prepared in 16 steps from a D-glucopyranose derivative (11) via the lactone 18. The key step is the introduction of the C-29 asymmetric carbon via hetero-conjugate addition at neighbouring spiro ethers.