Bulky derivatives of boranes, boronic acids and boronate estersvia reaction with diazomethanes

Abstract

Reactions of the perfluoroarylboranes RB(C₆F₅)₂ (R = C₆F₅, Ph, Cl, OC₆F₅) with Me₃SiCH(N₂), (C₆F₅)CH(N₂) or Ph₂C(N₂) yield (C₆F₅)₂B(Me₃SiCH(C₆F₅)) 1, (C₆F₅)B(Me₃SiCH(C₆F₅))₂2, (C₆F₅)B(Me₃SiCH(C₆F₅))(Me₃SiCH(C₆H₅)) 3, (C₆F₅)₂B(CH(C₆F₅)₂) 4, ClB(C₆F₅)(Ph₂C(C₆F₅)) 5 and (C₆F₅O)B(C₆F₅)(Me₃SiCH(C₆F₅)) 6 as a result of single or double insertion of a Me₃SiCH, C₆F₅CH or Ph₂C fragment into a B–C bond of the respective borane. Reactions of one or two equivalents of ethyl α-diazomethylacetate with B(C₆F₅)₃ yielded (Me)(C₆F₅)(CC)(OC₂H₅)(OB(C₆F₅)₂) 8 and [(Me)(C₆F₅)(CC)(OC₂H₅)]₂(O₂B(C₆F₅)) 9, in addition to the corresponding pyridine adducts (Me)(C₆F₅)(CC)(OC₂H₅)(OB(C₆F₅)₂)(py) 10 and [(Me)(C₆F₅)(CC)(OC₂H₅)]₂(O₂B(C₆F₅))(py) 11. Similarly, reaction of α-diazomethylacetate with BPh₃ yielded analogous products of borane reorganization, (Me)(C₆H₅)(CC)(OC₂H₅)(OBPh₂) 12 and was isolated as a mixture of E and Z-isomers whereas BPh₃ reacts with Me₃SiCH(N₂) and pyridine yielding (py)B(Ph₂(Me₃SiCH(Ph)) 7. Reactions of Ph₂C(N₂) with RB(OH)₂ (R = C₆F₅, p-F-C₆H₄, C₆H₅) yielded cyclic boroxines of the form [Ph₂C(R)BO]₃ (R = C₆F₅13, p-FC₆H₄14, C₆H₅15) while reactions of the boronate esters (C₆H₄O₂)BR (R = C₆F₅, p-F-C₆H₄) with three or five equivalents of Me₃SiCH(N₂) yielded (C₆H₄O₂)B(Me₃SiCH(Ar)) (Ar = C₆F₅16, p-F-C₆H₄17) and [(Py)B(C₆H₄O₂)(Me₃SiCH(Ar))] (Ar = C₆F₅18, p-F-C₆H₄, 19) upon complexation with pyridine. Reaction of HBCat and ClBCat with Ph₂C(N₂) yielded the products of B–H and B–Cl bond derivatization (C₆H₄O₂)B(Ph₂CR) (R = H 20, Cl 21), while the triethylphosphine oxide adduct (Et₃PO)B(C₆H₄O₂)(CPh₂Cl) 22, is readily isolable.