A cyclic (alkyl)(amino)bromoborane (CAABBr) was synthesized by a reaction of the corresponding hydroborane with bromine in the presence of triethylamine. Reduction of the resulting CAABBr with Li powder and 4,4'-di-tert-butylbiphenyl (DBB) generated a thermally labile cyclic (alkyl)(amino)boryllithium (CAABLi) which was characterized by NMR spectroscopy. Quenching of the mixture reduced by Li/DBB with methanol-d(1) or MeOTf at low temperature gave a deuterioborane or methylborane, supporting the generation of CAABLi.