Methylation and protonation of 1-aza-5-bora-4,6,11-trioxabicyclo[3.3.3]undecane and 1-aza-5-borabicyclo[3.3.3]undecane

Abstract

1-Aza-5-bora-4,6,11-trioxabicyclo[3.3.3]undecane (triethanolamine borate) reacts with methyl trifluoromethanesulfonate (triflate) with cleavage of one of the B–O bonds to give 1-(2-methoxyethyl)-1-aza-5-bora-4,6-dioxabicyclo[3.3.0]octan-1-ium triflate, but protonation occurs on nitrogen with cleavage of the intrabridgehead B–N bond. 1-Aza-5-borabicyclo[3.3.3]undecane is unaffected by methyl triflate or triflic acid in dichloromethane or acetonitrile, but undergoes B–C cleavage in neat triflic acid.