Boraalkenes Made by a Hydroboration Route: Cycloaddition and B=C Bond Cleavage Reactions

Authors:
Publisher website
Google Scholar
Abstract
Hydroboration of styrene or vinylcyclohexane with the IMes(C6F5)BH+ cation followed by deprotonation provided a convenient synthetic entry to the [B]=CHCH2R boraalkenes 9 a and 9 b. The in situ generated IMes(SCN)BH+ system reacted similarly with 1,1‐diphenylethene followed by deprotonation to give the isothiocyanato substituted boraalkene 9 c. The boraalkenes underwent [2+2] cycloaddition reactions with a small series of heterocumulenes to give the respective four‐membered heterocycles. The [B]=CHCH2R+CO2 cycloadducts 13 a and 13 b added the borane HB(C6F5)2 with cleavage of the central B−C σ‐bond. CS2 underwent an unusual reaction with the boraalkenes, namely insertion into the B=C bond with formation of the borylated dithioketene acetal under complete rupture of the strong B=C double bond. The intermediate dithiobora‐β‐lactone type intermediate was isolated in the case of the isothiocyanato‐boraalkene reaction and characterized by X‐ray diffraction.
Funding Information
  • Alexander von Humboldt-Stiftung

This publication has 62 references indexed in Scilit: