Synthesis and Phosphorylation of 4-Functionalized 2-tert-Butyl-3-chloromethylfurans

摘要

3-Ethoxycarbonyl- and 3-acetyl-2-methyl-5-tert-butylfurans undergo chloromethylation under the unusually rigorous conditions (55-60 deg C, 3-3.5 h). The corresponding diethylamide and nitrile were prepared by standard modification of the carboxy group. In phosphorylation of the resulting chloromethylfurans under the conditions of the Michaelis-Becker reaction, in the case of the ester and diethylamide, the phoshonate yields wee close to those obtained with compounds containing no tert-butoxy group, and in the case of acetylfuran the yield was even somewhat higher. On the contrary, the chloromethylated nitrile reacts considerably more slowly than all the other compounds under consideration and than the similar compound containing no tert-butyl substituent. Thus, the effect of the tert-butyl group in the #alpha#-position of the furan ring is clearly pronounced in the electrophilic substitutions in the neighboring position of the heteroring. When the reaction center is located in the side chain (substitution of chlorine), the effect of the bulky substituent is manifested only in special cases and can be attributed to the presence of a conformation in which the chloromethyl group is shielded.