- Synthesis of optically active (2-arylvinyl)glycine derivatives by palladium-catalyzed arylation of (s)-n-(benzyloxycarbonyl)vinylglycine
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Phenyl, tolyl, anisyl, and 1-naphthyl iodides (7a-g,n) smoothly reacted with (S)-N-(benzyloxycarbonyl)-vinylglycine (6) in H2O in the presence of Pd(OAc)2, Bu4NCI, and NaHCO3 at 45°C, producing [S-(E)]-(2- arylvinyl)glycine derivatives 8a-g, n of high enantiomeric purity. The yields of the reactions of 3- (7f), 2- (7e), and 4-iodoanisoles (7g) increased in this order. This relationship between the yield and the position of substitution has been found to hold for bromophenyl iodides (7i-k), although somewhat lower chemical and optical yields were realized in these cases. Phenyl iodide 71 carrying an electron-withdrawing 4-acetyl group gave an unsatisfactory result, and more electron-deficient 4-nitrophenyl iodide (7m) did not provide the desired product. All these results suggest that the reaction is advantageous with electron-sufficient substrates 7. However, this was not the case for 4-iodophenol (7h), as well as some heterocyclic iodides.
- Itaya, Taisuke,Hozumi, Yoshitaka
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p. 1094 - 1101
(2007/10/03)
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- The Heck reaction of N-protected vinylglycines with 4-iodoanisole
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Among N-protected and unprotected vinylglycines tested, N-(benzyloxycarbonyl)vinylglycine (1c) provided the highest yield of the coupling product 3c in the reaction with 1-iodo-4-methoxybenzene (2) in N,N-dimethylformamide in the presence of palladium acetate, sodium bicarbonate, and tetrabutylammonium chloride, whereas none of the desired product was obtained in the reaction with 4-methoxyphenyl trifluoromethanesulfonate (7). The stereo-selectivity of the reaction was reversed by employing triethylamine instead of sodium bicarbonate to furnish (Z)-3c predominantly. In the presence of sodium bicarbonate, replacement of the solvent by water improved not only the chemical yield and stereo-selectivity but also the optical purity: geometiically pure (E)-3c of 96% ee was formed in a good yield.
- Itaya,Shimizu
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p. 398 - 402
(2007/10/02)
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