Menthyl vinyl ether

However, most asymmetric 1,3-dipolar cycloaddition reactions of nitrile oxides with alkenes are carried out without Lewis acids as catalysts using either chiral alkenes or chiral auxiliary compounds (with achiral alkenes). Diverse chiral alkenes are in use, such as camphor-derived chiral N-acryloylhydrazide (195), C2-symmetric l,3-diacryloyl-2,2-dimethyl-4,5-diphenylimidazolidine, chiral 3-acryloyl-2,2-dimethyl-4-phenyloxazolidine (196, 197), sugar-based ethenyl ethers (198), acrylic esters (199, 200), C-bonded vinyl-substituted sugar (201), chirally modified vinylboronic ester derived from D-( + )-mannitol (202), (l/ )-menthyl vinyl ether (203), chiral derivatives of vinylacetic acid (204), ( )-l-ethoxy-3-fluoroalkyl-3-hydroxy-4-(4-methylphenylsulfinyl)but-1 -enes (205), enantiopure Y-oxygenated-a,P-unsaturated phenyl sulfones (206), chiral (a-oxyallyl)silanes (207), and (S )-but-3-ene-1,2-diol derivatives (208). As a chiral auxiliary, diisopropyl (i ,i )-tartrate (209, 210) has been very popular. 

In order to investigate in more detail the relationships between structure and photoinitiation activity in the polymeric systems based on benzoin methyl ether moieties, poly(MBA) and copolymers of MBA with menthyl acrylate [poly(MBA-co-MtA)s] have also been checked as photoinitiators and compared with the homopolymer of ot-vinyloxymethylbenzoin methyl ether and its copolymers with menthyl vinyl ether [poly(MBVE) and poly(MBVE-co-MtVE)s, respectively] [61,84]. 

Dicls-Aldcr reactions of 2-pyroncs with reactive dienophiles can also be effected without decomposition by use of high pressure (8,254). This version has been used to effect cycloaddition of 3-acyloxy-2-pyrones with vinyl ethers at 25° to give bicyclic adducts in good yield.2 Use of chiral vinyl ethers can result in diastcreosclectivc reactions. The highest levels of induction are observed with 8-(/3-naphthyl)menthyl vinyl ether and 8-(3,5-dimethylphenyl)mcnthyl vinyl ether (88 12). 

Also, in studies with optically active vinyl ethers it was observed [104] that trimethyl vinyl silane, which is bulky and non-chiral forms highly syndiotactic polymers. Equally bulky, but chiral (—)-menthyl vinyl ether, however, produces isotactic polymers in polar solvents. This suggests that isotactic propagation is preferred in a polar medium because of helical conformation of the polymer... 

Poly(maleic anhydride-co-acrylic acid), grafting to poly(ethylene-co-vinyl acetate), 683 Poly(maleimides), 91 physical properties, 265 Poly(/-menthyl vinyl ether-alt-MA), optically active polymer, 317 Polymer blends... 

Menthyl vinyl ether polymers of the diastereomer-ic menthols (-I-)-menthol, (-1-)-isomenthol and (-I-)-neomenthol have been synthesized and studied. While the menthyl and the neomenthyl derivatives both showed enhanced VCD features compared to the... 

H-NMR spectra in the aromatic proton region of copolymers of NVC with (—)-menthyl vinyl ether and with dialkyl fumarates having different chemical compositions. In the former copolymer samples indication of the blocking tendency is evidenced by the significant shielding effect even in samples containing 10% of NVC units. 

Fig. 7. UV spectra in the 260-225 nm region of copolymers of N-vinylcarbazole (NVC) and (—)-menthyl vinyl ether (16) having different composition and of 9- o-propylcarbazole (NIPC)...

Fig. 11. Corrected fluorescence spectra normalised at 370 nm of copolymers of N-vinyl-carbazole (NVQ with (—)-menthyl vinyl ether having different NVC content and of 9-iso-propylcarbazole (NIPQ...

Fig. 12. Trends of relative intensity (I) of different components of fluorescence spectra of copolymers of N-vinylcarbazole (NVQ with (—)-menthyl vinyl ether vs. NVC content — — monomer —H— high energy excimer —A—low energy excimer...

Fig. 13. UV and CD spectra in iso-octane of (—)-menthyl vinyl ether/N-vinylcarbazole (NVC) copolymer containing 17 % of NVC units...

For all copolymers of NVC with optically active menthyl derivatives the variation in induced circular dichroic absorption exhibits a maximum with increasing NVC content. For copolymers of NVC and (—)-menthyl vinyl ether this maximum is very pronounced and occurs at approximately 20% NVC content . Copolymers of NVC with (—)-menthyl acrylate and (—)-menthyl methacrylate show rather similar maxima, at about 40% and 50% NVC contents respectively. Typical trends are shown in Fig. 16. 

The results suggest that a maximum in induced circular dichroism arises from the optimization of sequence lengths of chiral and prochiral units. This seems to originate from the interposition of relatively short NVC sequences (two-four units) in relatively long sequences of the chiral monomer (three or more units). Copolymers with (—)-menthyl vinyl ether have been shown to be block-like in nature and as a consequence a significant amount of short sequences of NVC units is achievable only at very high (—)-menthyl vinyl ether contents. In the case of free radically prepared copolymers of NVC and ( )-menthyl acrylate it is necessary to have an NVC content of approxi-... 

Nitrile oxides are relatively electron-deficient compounds that react smoothly with electron-rich vinyl ethers. Jenkins and co-workers (171) investigated the reactions of L-menthyl-, 8-phenylmenthyl- and S)-endo- >omy vinyl ethers with nitrile oxides, but generally the de values were <33%. However, use of the chiral vinyl ether 114 in the reaction with a number of alkyl and benzonitrile oxides provided product 115 with de values of up to 66% (Scheme 12.38). It is proposed that the syn-staggered conformation is preferred for the vinyl ether 114 as indicated... 

In agreement with the data on poly-a-olefins and poly-vinyl-ethers having the side chain asymmetric carbon atoms in the y-position with respect to the main chain, stereoregularity does not exert a remarkable influence on the rotatory power of poly-acrylates and poly-methacrylates. In fact, according to the quantitative data reported by H. Sobue, K. Matsuzaki, S. Nakano (135), and to the qualitative indications given by Liu, Szuty and Ullmann (64), concerning respectively poly-menthyl-meth-acrylate and poly-(l-methyl-benzyl)-methaciylate, the specific optical activity of the polymers does not vary by more than 30% when varying, within a wide interval, the isotactic triads content of the polymers (Table 18). 

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