A useful synthetic sequence

Figure 1. From Ref [1].

This is a very useful synthetic sequence for partially saturated piperidines. The reactions can be done in a one-pot manner to furnish a nitrile group (TMSCN) or allyl functionality (Ally-TMS) on the piperidine system. Both of these functionalities have great synthetic potentials: the nitrile can be hydrolyzed to afford carboxylic acid derivatives and the allyl group can be seen as a handle for other transformations (e.g. extension).


Figure 2. From Ref [1].

Asymmetric version is also possible and the authors’ rationale is presented in Figure 2. Note the highly organized transition state to ensure good enantioselectivity.

Reference:
[1]. Synthesis of 1,2,4-trisubstituted-1,2,5,6-tetrahydropyridines
Meng-Yang Chang , Ming-Fang Lee, Nien-Chia Lee, Yu-Ping Huang, Chung-Han Lin
Tetrahedron Letters 52 (2011) 588–591