Propenyl Ether Research Articles

Combination of 17O and 13C NMR spectra of isomeric allyl and (Z)-propenyl ethers with their relative thermodynamic stabilities

The 17O NMR spectra of ten allyl ethers ROCH 2CHCH 2 and those of the isomeric (Z)-propenyl ethers ROCHCHMe, where R is an alkyl group or a MeO-substituted alkyl group, were recorded in CDCl 3 solution. The difference in 17O NMR chemical shift between a propenyl ether and the isomeric allyl ether, ca. 50 to 60 ppm, depends primarily on the number of MeO groups attached to the α carbon of the R moiety, and is related to the strength of p-π conjugation in the propenyl ether. Previous 13C NMR shift data for the β olefinic carbon of the propenyl ethers and the thermodynamic data of isomerization of allyl ethers to propenyl ethers are discussed in view of their relation to the 17O NMR shift data.

Synthesis and Photopolymerization of Multifunctional Propenyl Ether Monomers

Synthesis and Photopolymerization of Multifunctional Propenyl Ether Monomers

Study of the Cationic Photopolymerization of Multifunctional Propenyl Ether Monomers

Study of the Cationic Photopolymerization of Multifunctional Propenyl Ether Monomers

Propenyl ethers. III. Study of the photoinitiated cationic polymerization of propenyl ether monomers

AbstractThe effects of photoinitiator structure and variations in the experimental parameters on the rate and extent of the photoinitiated cationic polymerization of propenyl ether monomers were studied. It was found that the photoinitiators can be divided into two classes: those which exhibit an induction period and those which do not. It was demonstrated that in those propenyl ether polymerizations using iodonium salts and certain sulfonium salts which do not have an induction period, a free radical chain‐induced decomposition of the onium salt takes place. The reactivity of a particular onium salt photoinitiator was shown to be related to its reduction potential. It was also shown that the structure of the monomer plays a major role in the free radical induced decomposition reaction. © 1993 John Wiley & Sons, Inc.

Propenyl ethers. II. Study of the photoinitiated cationic polymerization of propenyl ether monomers

AbstractThe results of studies of the photoinitiated cationic polymerization of mono‐, di‐, and multifunctional propenyl ethers are reported in this article. Real‐time infrared spectroscopy and differential scanning photocalorimetry were used to determine the reactivity of the monomers with respect to each other and in relation to other types of cationically polymerizable monomers. Propenyl ethers were observed to be highly reactive monomers in photoinitiated cationic polymerization undergoing very high conversions to polymer at very short irradiation times. Attempts were also made to correlate the structures of these monomers with their reactivity as well as to examine the effects of various experimental parameters on their photopolymerization. © 1993 John Wiley & Sons, Inc.

The synthesis of 4-(2,6,10-trimethyl-1,3,5,9-undecatetraenyl)benzoic acid based on alkoxy alkene-acetal condensation

4-(2,6,10-Trimethyl-1,3,5,9-undecatetraenyl)benzoic acid (1) was synthesized starting from ethyl 4-formylbenzoate (2) and linalool. The key intermediate, ethyl 4-(2-methyl-3-oxo-1-propenyl)benzoate (5), was obtained by the addition of diethyl acetal (3), prepared from2, to ethyl 1-propenyl ether (EPE) followed by the hydrolysis of the resulting adduct.

Propenyl ethers. I. The synthesis of propenyl ether monomers

AbstractA variety of mono‐, di‐, and multifunctional propenyl ethers were readily prepared in high yields by the condensation of alcohols with allyl halides followed by the base or transition metal‐catalyzed rearrangement of the corresponding allyl ethers. Their straightforward synthesis and high reactivity in cationic UV curing make these monomers highly attractive for a variety of applications. The successful photopolymerization of these monomers has required the synthesis of specially tailored onium salt photoinitiators. © 1993 John Wiley & Sons, Inc.

Tandem inter [4+2]/intra [3+2] nitroalkene cycloadditions. 4. Cycloadditions with (E)- and (Z)-1-propenyl ethers

The tandem [4+2]/[3+2] cycloaddition of nitroalkene 1 was initiated efficiently by 1-propenyl ethers as the dienopile. Ethyl (E)-1-propenyl ether reacted highly selectively to give a single nitroso acetal cycloadduct 6. Hydrogenolysis of 6 afforded a single isomer of α-hydroxy lactam 8 wherein the newly installed methyl group occupied the β-configuration. Similarly, ethyl (Z)-1-propenyl ether produced an anomeric mixture of cycloadducts 7a and 7b witch afforded a single α-hydroxy lactam 9 upon hydrogenolysis.The methyl group in 9 occupied the α-orientation.The high and complementary selectivity for production of 8 and 9 was explained on the basis of an extreme endo preference for the ethoxy group of the 1-propenyl ether in the [4+2] cycloaddition

Relative thermodynamic stabilities of isomeric alkyl allyl and alkyl ( Z)-propenyl ethers

The relative thermodynamic stabilities of ten allyl ethers (ROCH 2CHCH 2) and the corresponding isomeric ( Z)-propenyl ethers (where R is an alkyl group, or a methoxysubstituted alkyl group) have been determined by chemical equilibration in DMSO solution with t-BuOK as catalyst. From the variation of the equilibrium constant with temperature, the values of the thermodynamic parameters ΔGΘ, ΔHΘ and ΔSΘ of isomerization at 298.15 K were evaluated. The propenyl ethers are highly favored at equilibrium, the values of both ΔGΘ and ΔHΘ for the allyl → propenyl reaction being ca. −18 to −25 kJ mol −1. The favor of the propenyl ethers is increased by bulky alkyl substituents, and decreased by methoxy-substituted alkyl groups. In most cases the entropy contribution is negligible; however, for R = (MeO) 2CH and R = (MeO) 3C the values of ΔSΘ are ca. −5 J K −1 mol −1.

Isomerization of 2-(allyloxymethyl)benzofurans and -benzothiophenes in the presence of potassium tert-butylate

When 2-(allyloxymethyl)benzofurans and -benzothiophenes react with potassium tert-butylate in dimethyl sulfoxide (DMSO), they isomerize to the corresponding propenyl ethers and also undergo the Wittig rearrangement to isomeric butenols.

Cationic polymerization of selected α- and β-substituted vinyl ethers

The cationic polymerization of various α- and β-substituted vinyl ethers, initiated by 1-iodo-1-(2-methylpropyloxy)ethane 1 and tetrabuty lammonium perchlorate (TBAP) was investigated. The polymerization of 2,3-dihydrofuran (DHF, 3a) in CH2Cl2 at -40°C proceeds via opening of the ethylenic double bond and yields polymers with narrow molar mass distributions and high glass transitions. The number average of molar mass increased linearly with conversion. Under these conditions, a controlled polymerization of two propenyl ethers (1-ethoxypropene 2a and 2-methoxypropene 2b) and two other cyclic unsaturated ethers (3,4-dihydro-2H-pyran 3b and 5-methyl-2,3-dihydrofuran 3c) could not be achieved. Either transfer reactions or the decomposition of 1 prevented the formation of high molar mass polymers of these vinyl ethers.

Intramolecular trapping of difluoroalkyl radicals by tethered olefin in the asymmetric synthesis of 2,4-disubstituted-3,3-difluorotetrahydrofurans

Optically pure propenyl ethers of 3-sulphenyl-, 3-sulphinyl-, and 3-sulphonyl-1-chloro-1,1-difluoropropan-2-ols were submitted to radical cyclization affording, with moderate to high diastereoselectivity. 3,3-difluorotetrahydrofurans containing in 2 and 4 positions various substituents. Detailed NMR analysis allowed to measure trans/cis ratios and to establish the structure of the products.

The electron-deficient olefin 2,2-bis(trifluoromethyl)ethylene-1,1-dicarbonitrile: hydride abstractions from allyl and isobutenyl ethers and thioethers

The title compound (BTF) combines with isobutenyl and methallyl ethers and thioethers furnishing the same formal insertion products 5; an ion pair arising from hydride transfer is proposed as a common intermediate. Allyl ethers (and thioethers) are subject to the same reaction whereas the isomeric propenyl ethers undergo [2+2] cycloaddition with BTF. The rate constant for the reaction of ethyl methallyl ether and BTF shows only a modest dependence on solvent polarity

Retention of optical activity in the [3,3]-sigmatropic rearrangement of a vinyl furfuryl ether

(−)-1-(2-Furyl)ethyl 2-propenyl ether undergoes a [3,3]-sigmatropic rearrangement with the formation of (+)-2-(2-ethyl-3-furyl)propanol, which indicates an at least partially concerted reaction mechanism.

ChemInform Abstract: De novo Synthesis of Carbohydrates and Related Natural Products. Part 32. The Inverse Type Hetero‐Diels‐Alder Reaction for the Synthesis of Partial Structures of Polyketide Natural Products.

AbstractInverse‐type hetero‐Diels‐Alder reaction of the compound (I) as heterodiene with the (Z) propenyl ether (II) as dienophile affords in an endo‐specific cycloaddition reaction the persubstituted dihydro‐2H‐pyran (III).

2 + 2] cycloaddition of optically active ketenes. Synthesis of (−)‐blastmycinone. Preliminary Communication

Abstract[2 + 2] Cycloaddition of (menthyloxy)methylketene (2) to cis‐ethyl propenyl ether showed a ca. 3:1 diastereo‐selectivity. A two‐step transformation of the thermodynamically more stable adduct 4 furnished the (2R*, 3R*)‐compound 5 with ca. 50% e.e. (Scheme 1). The analogous reaction sequence with cis‐ benzyl 1‐hexenyl ether (9) and 2 showed a ca. 5:1 diastereoselectivity in 10 and 11 (Scheme 2). Absolute configuration of C(3) and C(4) in 11 has been proved by converting it to (−)‐blastmycinone. Accordingly, the preferred transition state has been deduced as 15.

Living cationic polymerization of cis‐ and trans‐ethyl propenyl ethers and synthesis of block copolymers with isobutyl vinyl ether

AbstractThe cationic polymerization of cis‐ and trans‐ethyl propenyl ethers (EPE, CH3CHCHOC2H5), initiated by a mixture of hydrogen iodide and iodine (HI/I2 initiator) at −40°C in nonpolar media (toluene and n‐hexane), led to living polymers of controlled molecular weights and a narrow molecular weight distribution (MWD) (M̄w/M̄n = 1.2–1.3). The geometrical isomerism of the monomer did not affect the living character of the polymerization. 13C NMR stereochemical analysis of the polymers showed that the living propagating end is sterically less crowded than nonliving counterparts generated by conventional Lewis acids (e.g., BF3OEt2). New block copolymers between EPE (cis or trans) and isobutyl vinyl ether were also prepared by sequential living polymerization of the two monomers.

Poly(vinyl ether)s and poly(propenyl ether)s containing mesogenic groups: A new class of side‐chain liquid‐crystalline polymers

AbstractA new series of thermotropic liquid‐crystalline polymers, poly(vinyl ether)s and poly(propenyl ether)s, containing the mesogen 4‐methoxy‐4′‐hydroxybiphenyl in the side chain and different spacers between the mesogens and the backbone were synthesized and characterized by DSC and optical microscopy. Their mesomorphic behavior was compared to that of the corresponding polymethacrylates. In general the poly(propenyl ether)s showed lower transition temperatures and larger thermal stability ranges of their mesophases than the respective polymethacrylates, reflecting the effect of substituting the rigid ester bond connecting the spacer to the backbone in polymethacrylates by a more flexible ether bond. Also, poly(propenyl ether)s showed more ordered mesophases than the polymethacrylates, suggesting that a better decoupling of the mesogen and polymer backbone is obtained through the ether linkage.

Living cationic polymerization of vinyl monomers: Mechanism and synthesis of new polymers

AbstractThis paper reviews the recent progress in our research on the living cationic polymerization of vinyl compounds by the hydrogen iodide/iodine (HI/I2) initiating system, with emphasis on its scope, mechanism, and applications to new polymer synthesis. The scope of the living cationic polymerization has been expanded to include vinyl ethers, propenyl ethers, unsaturated cyclic ethers, and styrene derivatives as monomers. The initiation/propagation mechanism was discussed on the basis of recent direct analysis on the living system by NMR and UV/visible spectroscopy. The proposed mechanism involves a quantitative formation of Hl‐vinyl ether adduct [CH3‐CH(OR)‐I; l] that is by itself incapable of initiating polymerization. In the presence of iodine, however, the CH‐I bond of l is electrophilically activated by iodine and living propagation occurs via the insertion of vinyl ether to the activated CH‐I bond. Such living polymerizations were found to proceed in not only nonpolar but polar solvents (CH2Cl2) as well. Quenching the living end with amines gave polymers capped with an amino group that in turn enabled us to determine the living end concentration. Applications of the HI/I2‐initiated living process to the synthesis of new bifunctional and block polymers were also described.

ChemInform Abstract: Tandem Alkylation‐Reduction. Highly Stereoselective Synthesis of (E)‐1‐Hydroxymethyl Methyl Propenyl Ethers from Aldehydes Using 1‐Lithio‐1‐methoxyallene.

AbstractDie im Titel genannten Verbindungen (IV) werden in einer Eintopfreaktion durch Umsetzung der Aldehyde (I) mit dem aus Methoxyallen (II) in situ erzeugten Lithium‐Derivat (VI) und nachfolgender Reduktion der Allene (III) mit Lithium in Ammoniak erhalten.