TOWARDS 2-SILAALLENES - SYNTHESIS OF SPIROCYCLIC PRECURSORS

Reactions of dichlorodivinylsilane (2) and LitBu in a molar ratio 1/1 and 1/2 lead to highly reactive intermediates, which can be trapped by suitable reagents. In the presence of trimethylmethoxysilane, norborn adiene, anthracene and diphenylacetylene, products are formed that pro vide evidence for the intermediate formation of both the neopentylsile ne H2C= CH(CI)Si = CHCH(2)tBu (3) and the 2-silaallene tBuCH(2)CH=Si=C HCH(2)tBu (4). The formation of double cycloadducts from 4 is particul arly interesting as a preparatively facile route for the synthesis of silaspirocycles such as 13, 16 and 17, which have been characterized b y single-crystal X-ray structure analysis.