Mechanistic exploration of the palladium-catalyzed process for the synthesis of benzoxazoles and benzothiazoles.

A convenient one-pot palladium-catalyzed cascade process for the preparation of both benzoxazoles and benzothiazoles has been developed. While these reactions proceed to give similar compounds the mechanisms governing the processes are different as are the experimental conditions employed.

Mild and Diazo-Free Synthesis of Trifluoromethyl-Cyclopropanes Using Sulfonium Ylides.

The synthesis of several 1,1-disubstituted trifluoromethyl-cyclopropanes (TFCPs), known as tert-butyl bioisosteres, has been achieved from the reaction between trifluoromethylalkenes and unstabilized sulfonium ylides in yields of ≤97%. This method offers practical access to this cyclopropyl moiety of pharmacological interest, employing a commercially available reagent at low temperatures. The synthesis of cyclopropanes bearing other electron-withdrawing groups as well as trisubstituted TFCPs was also accomplished.

Short Approach toward the Nonracemic A,B,E Tricyclic Core of Calyciphylline B-Type Alkaloids.

A suitably functionalized tricyclic adduct containing the common A,B,E rings found in calyciphylline B-type alkaloids was obtained in nine linear steps. The key transformation features an efficient one-pot sequence of intramolecular Vilsmeier-Haack cyclization and azomethine ylide 1,3-dipolar cycloaddition in which three cycles, three new carbon-carbon bonds, and three stereocenters are formed, one being fully substituted. This work also demonstrates the first use of a chiral, nonracemic cyclic enol ether as an internal carbon nucleophile.

A powerful palladium-catalyzed multicomponent process for the preparation of oxazolines and benzoxazoles.

Efficient and convenient three-component couplings of an aryl halide, isocyanide, and an amino alcohol under palladium catalysis provide a range of oxazolines and benzoxazoles in excellent yield.