ABSTRACT
Azetidine and oxetane sulfinate salts are easily prepared from commercially available 3-iodoheterocycle precursors in a three-step sequence. They undergo smooth coupling reactions thereby providing an expedient route for the introduction of these four-membered heterocycles into indoles.
Subject(s)
Azetidines/chemical synthesis , Ethers, Cyclic/chemical synthesis , Indoles/chemistry , Sulfinic Acids/chemistry , Oxidation-Reduction , SaltsABSTRACT
Significant rate enhancements in the Diels-Alder reaction of alkynes and 2-pyrones bearing a Lewis basic group are observed when a combination of alkynyltrifluoroborates and BF3·OEt2 is used. This process generates functionalized aromatic compounds with complete regiocontrol. The observed rate enhancement was studied by density functional theory methods and appears to originate from coordination of the diene substrate to a mixture of alkynylborane intermediates, followed by a Lewis acid-mediated product equilibration step. Evidence for this mechanism is presented, as is the enhanced promotion of the cycloaddition via the use of alternative Lewis acid promoters.
