“…[16,17,34,35,36] The identity of the dominant acyloxyborohydride reducing species depends largely on the molar ratio between carboxylic acid and the borohydride, though exact determination of the dominant species is difficult. [16,17,[37][38][39] Generally, triacyloxyborohydrides are the most easily prepared and characterized, though other stable mono- [37,38] and diacyloxyborohy- dride [39] species have been reported. In our procedure, TarB-NO 2 and NaBH 4 are used in equimolar amounts, which would tend to favor the formation of a single monoacyloxyborohydride moiety per TarB-NO 2 molecule (Scheme 2).…”