CHEMISTRY OF BORON .226. FUNCTIONALIZATION OF ALKYNYLBORANE REACTIONSWITH NUCLEOPHILES

The synthesis of alkynylboranes RR'B-C drop C-R '' 1-3 and their react ions with various nucleophiles are described (R, R'= Me(2)N, Cl, alkyl ; R '' = Me, Ph). Although these compounds can be looked upon as inorg anic Michael systems, nucleophiles such as alcohols, amines, amides an d various carbon nucleophiles attack exclusively at the boron atom (an alogous to a 1,2 attack). Thus, a convenient means of functionalizatio n of alkynylboranes at the boron atom with preservation of the B-C dro p C moiety is described, and alkynylboranes with R, R' = Me(2)N, N(H)P r-i, pyr, (OPr)-Pr-i, Me, Mes, C drop C-SiMe(3) were obtained in good yield and characterized by spectroscopic methods. The pathway for the reaction of (Me(2)N)(2)B-C drop C-Ph with carbon nucleophiles to tris( alkyl)boranes has been elucidated. The implications both for the elect ronic properties and the chemical reactivity of alkynylboranes are dis cussed.