Synthesis of Substituted Cyclic Ethers from Halo Ketones and Halo Aldehydes by Palladium-Catalyzed Coupling with Organotin Reagents

Article abstract of DOI:10.1021/jo00172a037

The palladium-catalyzed reaction of a variety of halo ketones or halo aldehydes with acetonyl- and allyltin reagents gives cyclic ethers in good yields.Oxiranes, oxetanes, and tetrahydrofurans can be obtained under mild reaction conditions.The use of palladium catalyst containing chiral monophosphine ligands gave a small enantiomeric excess (up to 19percent) of a chiral oxirane from an α-halo ketone.The allyl- and acetonyloxirane products tend to undergo further transformations in prolonged reactions: allyloxiranes rearrange to α-allyl aldehydes and acetonyloxiranes dehydrate to give substituted furans.The mechanism of the reaction appears to involve addition of the organotin ligand to the carbonyl, followed by palladium(II)-catalyzed cyclization of the tin alkoxides.