Novel generation of azomethine imines from α-silylnitrosamines by 1,4-silatropic shift and their cycloaddition
摘要:
Novel and facile generation of azomethine imines from alpha-silylnitrosamines and subsequent cycloaddition with dipolarophiles leading to a variety of pyrazole derivatives have been developed. The key to the reaction is a 1,4-silatropic shift caused by strong affinity of the nitroso oxygen atom toward the silicon atom. Thus, alpha-silylnitrosamines are treated with 1 equiv. of dipolarophiles in refluxing toluene for 1 h to give pyrazole derivatives in good to excellent yields. (C) 1999 Elsevier Science Ltd. All rights reserved.
A general, versatile method for alkylation and arylation of haloheterocyclic compounds is reported. In the presence of a catalytic quantity of [NiCl2(dppp)], where dppp stands for Ph2P(CH2)3PPh2, bromothiophenes, halopyridines, haloquinoline, and haloisoquinolines reacted with alkyl and aryl Grignard reagents at room temperature or at ether refluxing temperature to give the cross-coupling products