2 ’ -hydroxyacetophenone Michael addition

The bis-prolinol-derived phenol (156) has been designed to facilitate the formation of heterodinuclear complexes based upon the large difference in pKH of the phenolic OH group and the tertiary OH groups. The first examples of its application involve hydroxyacetophenones (157) as donors in the asymmetric Michael addition to nitroalkene acceptors (158) the best stereocontrol was observed with a zinc- magnesium dinuclear complex, where enantiomeric excesses ranged up to 92% for the major anti diastereoisomer (159).212... 

Acylketene dithioacetal 107 and the corresponding /3-methylthio-a,/3-enone 108 undergo self-condensation and aromatization in the presence of sodium hydride and methyl benzoates in refluxing xylene to give 2,6-bis(methylthio)-4-hydroxyacetophenone (109) and 4-hydroxyacetophenone (110), respectively, in good yields (equation 103) . The possible pathway for the formation of 109 and 110 could involve base-catalysed condensation of either 107 or 108 with methyl benzoates followed by successive inter-and intramolecular Michael additions and elimination of SMe. No reaction is observed in the absence of methyl benzoates. 

Flavanones 25 are often synthesized by Claisen-Schmidt condensation followed by intramolecular Michael addition reaction of the corresponding chalcone derivative. Climent et al. reported a new environment-friendly method to prepare flavanones 25 by the reaction of 5-substituted-2-hydroxyacetophenones and benzaldehydes using hydro-talcites as basic catalysts (Scheme 16) [81]. Substitution over both aromatic rings influenced the reaction coxu-se leading to flavanones 25 in 7-45% of yields in only Ih of reaction time. 

Corma et al. have also tested MCM-410H in the aldol condensation between benzaldehyde and 2 -hydroxyacetophenone. They showed that this material catalyzed successive aldol condensation and intramolecular Michael reaction addition to give flavone with good selectivity. Chromenes can be also produced by condensation of salicylaldehyde derivatives and diethylglucotaconate under mild conditions (Figure 9). 

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