Unsaturated C3B2-rings with neighboring boron atoms. Derivatives of 4-methylene-1,2-diboracyclopentane dilithium 2,3-diboratafulvene and 1,2-diboro-3-cyclopentene.
Methylenediboracyclopentanes I (R = Et, CHMe2) were prepd. by cyclocondensation of H2C:C[CH2BCl:NR2]2 in the presence of Na/K alloy. Reaction of I with lithium 2,2,6,6-tetramethylpiperidide or Me3CLi followed by cyclopentadiene gave II (R = Et, CHMe2, resp.). The x-ray crystal structure of I (R = CHMe2) was detd.
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