Silaheterocyclen, XXXIII [1, 2]: Cycloadditions-Reaktionen des 1.1-Dichlor-2-neopentyIsilaethens mit Pentafulvenen / Silaheterocycles, XXXIII [1, 2]: C y clo ad d itio n Reactions of 1.1-Dichloro-2 -neopentylsilene with Pentafulvenes

Abstract

The reaction between in situ formed 1.1-dichloro-2-neopentyl-1-silene, Cl2Si=CHCH2tBu (2), and 1,1-dimethylpentafulvene (5) leads to the formation of exo/endo-isomeric [4+2] cycloadducts 9 and [2+2] stereoisomers 10 in good yields. NMR spectroscopic investigations of the product mixture prove the different modes of the silene cycloaddition reactions ([4+2] vs [2+2] addition).Treatment of 9 and 10 with LiAlH4 and LiMe yield the stereo- and regioisomeric derivatives (LiAlH4: 16, 17: MeLi: 18. 19). whereas PhMgBr reacts with 10 to give only the mono substitution, the [4+2] compound 20. and the diphenylated silacyclobutane 21. The reactions of silene 2 with pentafulvenes 6-8 lead to similar results.