Piperidines multifunctional derivatives

The use of chiral chloroformates, such as that derived from tranx-2-(a-cumyl)cyclohexanol, allows diastereoselective additions to 4-methoxypyridine. The introduction of a tri-ixo-propylsilyl group at C-3 greatly enhances the diastereoselectivity. The products of these reactions are multifunctional chiral piperidines which have found use in the asymmetric synthesis of natural products. ... 

By employing the dienamine-catalysis strategy, Chen and coworkers accomplished an unprecedented and highly regio- and stereoselective inverse-electron-demand aza-hetero-Diels-Alder reaction of a,P-unsaturated imines 136 with a,P-unsaturated aldehydes 143 [66]. Various multifunctional piperidine derivatives 144 and 145 can be obtained, with excellent levels of enantioselectivity, that are potentially useful in the synthesis of natural products and medicinal chemistry (Scheme 38.43). 

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