Phosphazene Base-Catalyzed Intramolecular Hydroamidation of Alkenes with Amides.

A method for the synthesis of cyclic amides via phosphazene base-catalyzed intramolecular hydroamidation of amide alkenes was developed. The reaction using a catalytic amount of P4-base had a good functional group tolerance and a broad substrate scope and could also be used to synthesize lactam, cyclic urea, and oxazolidinone compounds. This catalytic system was expanded to a one-pot intramolecular hydroamidation and intermolecular hydroalkylation.

Total synthesis of natural enantiomers of heliespirones A and C via the diastereoselective intramolecular Hosomi-Sakurai reaction.

A full account of the development of a novel type of the intramolecular Hosomi-Sakurai reactions of the substrates with a p-benzoquinone and an allylsilane moieties connected by an ether linkage is described. This transformation proceeds via an addition-elimination sequence and provides the products with two stereogenic centers through a 1,3(or 1,4)-asymmetric induction in good to excellent diastereoselectivities. A reasonable mechanistic possibility for the reaction, determination of the stereochemistry for the product, and scope and limitation of the transformation are also discussed.