Facile 1,1-carboboration reaction of a diarylphosphino-substituted conjugated diyne with tris(pentafluorophenyl)borane

Abstract

Bis(dimesitylphosphanyl)butadiyne (14) reacts with B(C6F 5)3 by a 1,1-carboboration sequence. The selective attack at a single phosphanyl-alkyne moiety is observed. First a phosphirenium-borate zwitterion 15 is formed at r. t. Thermolysis (80 °C) results in the E-selective formation of the 1,1-carboboration product, the frustrated Lewis pair (FLP) E-16, which upon heating to 160 °C eventually undergoes isomerization followed by an internal nucleophilic aromatic substitution reaction to give the product 17 featuring a -B(F)(C6F 5)2 substituent at the five-membered P-heterocycle. Finally, the FLP E-16 was reacted with n-butylisocyanide to yield the five-membered heterocyclic product 18, formed by P,B addition to the isonitrile carbon atom. Compounds 14, 15, 17, and 18 were characterized by X-ray crystal structure analyses. © 2013 Verlag der Zeitschrift für Naturforschung, Tübingen.