Hydroboration of alkynylchlorosilanes as an efficient route for the synthesis of SiNNB heterocycles

Abstract

AbstractAlkenylsilanes bearing chlorosilyl and boryl groups geminally attached to a carbon atom ((E)‐3‐(9‐borabicyclo[3.3.1]nonan‐9‐yl)‐N,N‐dimethyl‐3‐(trichlorosilyl)prop‐2‐en‐1‐amine, 1, (1‐(9‐borabicyclo[3.3.1]nonan‐9‐yl)‐3,3‐dimethylbut‐1‐en‐1‐yl)dichloro (phenyl)silane, 2, (1‐(9‐borabicyclo[3.3.1]nonan‐9‐yl)‐2‐phenylvinyl) chloro (methyl)(phenyl)silane, 3, (1‐(9‐borabicyclo[3.3.1]nonan‐9‐yl)hex‐1‐en‐1‐yl)trichlorosilane, 4) are accessible by hydroboration of the corresponding alkynylsilanes. Only the vinyl group of 1 adopted E configuration, which may be favored by ring closure via an intramolecular B–N bonding interaction. Compounds 2–4 reacted with N‐trimethylsilylpyrazole and N‐2‐(trimethylsilylamino)pyridine by elimination of ClSiMe3 and formation of Si–N bonds. Intramolecular donor–acceptor interactions between the N and B atoms afforded five‐ and six‐membered heterocycles, which contained Si, N, and B as heteroatoms. A bis(pyrazolyl)silane was isolated upon treatment of a dichlorosilane with two equivalents of trimethylsilylpyrazole.