No abstract

The intramolecular acid catalyzed aldol cyclization of 2,3,7-triketoesters formed from ζ-keto-α-diazo-β-ketoesters provides highly functionalized cyclopentanones with good diastereoselectivity in high overall yields via kinetically controlled and stereodivergent catalytic processes. Lewis acid catalysis gives high selectivity for the 1,3-anti tetrasubstituted cyclopentanones, whereas Brønsted acid catalysis produces the corresponding 1,3-syn diastereomer.

The synthesis of α-carbonylimines by rhodium(II)-catalyzed reactions of α-diazoesters and organic azides has been developed and applied in hetero-Diels-Alder reactions to form highly functionalized tetrahydropyrimidines and in a one-pot, multicomponent transformation between aryldiazoacetates, p-anisyl azide, and an enonediazoacetate to produce β-lactams in high yields and diastereoselectivities.

Carbonyl-ene reactions of 2,3-diketoesters catalyzed by [Cu{(S,S)-tBu-box}](SbF6)2 [box=bis(oxazoline)] generate chiral α-functionalized α-hydroxy-β-ketoesters in up to 94% yield and 97% ee. The 2,3-diketoesters are conveniently accessed from the corresponding α-diazo-β-ketoester, and a catalyst loading as low as 1.0 mol% can be achieved.