Homoallylic hydroxy ketones synthesis

The synthesis of 11 jS-hydroxy-A -3-ketones (17) from A ° -compounds (16) has been carried out by the homoallylic hydroxyl-assisted Simmons-Smith reaction. 

The intramolecular Mannich reaction has been combined with the facile [3,3] sigmatropic rearrangement of iminium cations to provide a versatile synthesis of 3-acylpyrrolidines and other more complex ring systems containing this subunit.In the simplest case, a homoallylic amine with alkoxy or hydroxy substitution at the allylic site is allowed to react with an aldehyde in the presence of an equivalent or less of acid to yield substituted 3-acylpyrrolidine products (Scheme 50). The mild conditions of this transformation—which occurs at near ambient temperature and neutral pH—are apparent in the success of this sequence with labile aldehydes such as furfural. Ketones can be employed also in this case a two-step... 

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