Functionalization of Piperidine Derivatives for the Site‐Selective and Stereoselective Synthesis of Positional Analogues of Methylphenidate

Abstract

Abstract Rhodium‐catalyzed C−H insertions and cyclopropanations of donor/acceptor carbenes have been used for the synthesis of positional analogues of methylphenidate. The site selectivity is controlled by the catalyst and the amine protecting group. C−H functionalization of N ‐Boc‐piperidine using Rh 2 ( R ‐TCPTAD) 4 , or N ‐brosyl‐piperidine using Rh 2 ( R ‐TPPTTL) 4 generated 2‐substitited analogues. In contrast, when N ‐α‐oxoarylacetyl‐piperidines were used in combination with Rh 2 ( S ‐2‐Cl‐5‐BrTPCP) 4 , the C−H functionalization produced 4‐susbstiuted analogues. Finally, the 3‐substituted analogues were prepared indirectly by cyclopropanation of N ‐Boc‐tetrahydropyridine followed by reductive regio‐ and stereoselective ring‐opening of the cyclopropanes.