Polysubstituted cyclopentanones

Chiral imines have proved to be useful reagents in the synthesis of cyclic systems. For example, imines derived from (S)-( — )- and (R)-( + )-l-phenylethylamine 412 have been used in the preparation of optically pure polysubstituted cyclopentanone derivatives 414 (equation 87)252 and in enantioselective steroid synthesis (equation 88)253. 

Following similar iminium activation strategies using prolinol-derived organocatalysts, highly functionalized chiral cyclohexanone derivatives [192], dihydropyranone compounds [193], and polysubstituted cyclopentanones [194] have been also synthesized. 

Double Michael addition reactions of a,p-unsaturated aldehydes with a p-ketoester bearing a highly electron-deficient olefin unit afford polysubstituted cyclopentanones (Scheme 6.13). TMS-protected diphenylprolinol catalyzes this enantioselective cascade reaction to form cyclopentanone with four contiguous stereocenters [15]. 

Ma, A., Ma, D. (2010). Enantioselective synthesis of polysubstituted cyclopentanones by organocatalytic double Michael addition reactions. Organic Letters, 12, 3634-3637. 

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