Phosphoramidite cyclopentanone

Feringa s group has demonstrated that cyclopentene-3,5-dione monoacetals as 2-47 can also be successfully applied as substrates in an asymmetric three-component domino Michael/aldol reaction with dialkyl zinc reagents 2-48 and aromatic aldehydes 2-49 [17]. In the presence of 2 mol% of the in-sitw-generated enantiomeri-cally pure catalyst Cu(OTf)2/phosphoramidite 2-54, the cyclopentanone derivatives 2-51 were formed nearly exclusively in good yields and with high ee-values (Scheme 2.11). 

Hoffman and Carreira [31] reported a Rh-catalyzed asymmetric intramolecular hydroacylation of pent-4-enal substrates, providing P-substituted cyclopentanones in good yield and excellent selectivity by using chiral spiro phosphoramidite-alkene ligand (R)-29 (Scheme 29). 

Catalytic intramolecular hydroacylations are valuable reactions to create functionalized cyclopentanones. Thus, easily available aldehyde 419 was treated with a chiral rhodium(I) catalyst prepared in situ from phosphoramidite 420-(S)-Ll and [Rh(C2H4)2Cl], silver hexafluoro antimonate, and a phosphine such as MeP(tBu)2 as an activator cyclopentanone 421 was obtained in good yield and with 95% ee. Without the phosphine, no reaction occurred (Scheme 3.80) [131]. 

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