The synthesis of functionalized azepenes and piperidines bearing an α-cycloheptenone or benzotropone derivative has been accomplished through direct reductive cross-coupling of α-bromo eneformamides or enecarbamates with highly versatile α-bromo benzotropone derivatives, under cobalt catalysis. The coupling products have been further elaborated to other synthetically useful aza-heterocyclic frameworks.

The interception of carbolithiation-derived tertiary benzylic α-lithio piperidines with carbon electrophiles, under HMPA-mediated conditions, has led to the diastereoselective synthesis of vicinally functionalized piperidines bearing α-amino quaternary stereocenters.

The synthesis of α- and α,β-functionalized azepenes and dehydropiperidines from readily prepared α-selenonyl eneformamides or enecarbamates has been achieved through Fe-catalyzed α-substitutive deselenonation, β-regioselective lithiation/trapping, and Co-catalyzed reductive cross-coupling protocols.

Trapping of Carbolithiation-Derived Tertiary Benzylic -Lithio Piperidines with Carbon Electrophiles: Controlling the Formation of -Amino Quaternary and Vicinal Stereocenters. -The carbolithiation of 2-aryl N-Boc-piperidines (I) followed by quenching with MeOH gives rise to 3-alkylated trans-products with high diastereoselectivity. Trapping of organolithium intermediate with dimethyl sulfate leads to 2,2,3-trisubstituted piperidine (V). Carboxylic acid (IX) and esters (XIV) and (XVII) are prepared analogously using dry ice or corresponding chloroformates as electrophiles for the trapping step. -(BENG*, T. K.; FOX, N.; BASSLER, D. P.; ALWALI, A.; SINCAVAGE, K.; SILAIRE, A. W. V.; Org. Biomol. Chem. 13 (2015) 32, 8647-8651, http://dx.doi.org/10.1039/C5OB01371B ; Dep. Chem., Susquehanna Univ., Selinsgrove, PA 17870, USA; Eng.) -R. Staver 50-150