Kinetic Resolution of 2-Aryl-4-methylenepiperidines toward Enantioenriched Functionalizable Piperidine Fragments

The base n-BuLi with sparteine allows a kinetic resolution of N-Boc-2-aryl-4-methylenepiperidines. The 2,2-disubstituted products and recovered starting materials were isolated with high enantiomeric ratios. From VT-NMR spectroscopy and DFT studies, the rate of rotation of the N-Boc group is fast. Lithiation and trapping of the enantioenriched starting materials gave 2,2-disubstituted piperidines with retention of stereochemistry. Functionalization of the 4-methylene group led to a variety of 2,4-disubstituted piperidines without loss of enantiopurity that could be useful building blocks for drug discovery.

Automated summary

The kinetic resolution of N-Boc-2-aryl-4-methylenepiperidines using the base n-BuLi with sparteine as a catalyst has been achieved, yielding high enantiomeric ratios of the 2,2-disubstituted products and recovered starting materials. Further investigation revealed the fast rotation rate of the N-Boc group, and lithiation and trapping reactions of the enantioenriched starting materials gave rise to 2,2-disubstituted piperidines with retention of stereochemistry. Functionalization of the 4-methylene group led to a range of 2,4-disubstituted piperidines without loss of enantiopurity, offering potential as valuable building blocks in drug discovery.