Pent-4-enals, hydroacylation

This reaction competes with intramolecular hydroacylation of pent-4-enals to form cyclopen-tanones. In the case of exo- and ent/o-norborn-5-ene-2-carboxaldehyde (4) if treated with Wilkinson s catalyst [tris(triphenylphosphane)rhodium(I) chloride] only decarbonylation occurs. While the exo-aldehyde exo-4 leads to norbornadiene (5), the e fi o-aldehyde endo-4 reacts to form nortricyclene (6 tricyclo[2.2.1.0 ]heptane). These results support organometallic pathways and exclude radical intermediates, since here identical products should be formed. 

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). 

Intramolecular hydroacylation of 4-substituted pent-4-enals is catalyzed by Rh (I) complexes and leads to 3-substituted cyclopentanones. When the ligand of rhodium is (l ,2,S)-3.35 (X = CH2CH2) or even better (Ky or (S)-binap 3.43 (Ar = Ph), cycloalkanones are obtained with an excellent enantiomeric excess... 

In 2011, the Carreira group developed the Rh-catalyzed asymmetric intramolecular hydroacylation reactions of pent-4-enals 17 for the preparation of cyclopentanones 18 (Scheme 8.7). In this study, the biindane-derived phos-phoramidite/olefin ligand (R)-Ll was found to be highly efficient to promote... 

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