General Information. Commercial reagents were purified prior to use following the guidelines of Perrin and Armarego. 1 Organic solutions were concentrated under reduced pressure on a Büchi rotary evaporator. Chloroform was distilled from calcium hydride prior to use. Ethyl acetate was pre-dried with 4Å molecular sieves prior to use.

No abstract

The factors controlling the highly alpha-selective C-glycosylation of ribose derivatives were determined by examining the stereoselective reactions of 18 ribose analogues differing in substitution at C-2, C-3, and C-4. The lowest energy conformers of the intermediate oxocarbenium ions display the C-3 alkoxy group in a pseudoaxial orientation to maximize electrostatic effects. To a lesser extent, the C-2 substituent prefers a pseudoequatorial position, and the alkyl group at C-4 has little influence on conformational preferences. In all cases, the product was formed by stereoelectronically preferred inside attack on the lowest energy conformer.

A single Cu(II) catalyst without the addition of ligand or base couples a diverse range of nitrogen sources with alkynes and aldehydes bearing alkyl, halogenated, silyl, aryl, and heteroaryl groups. The first example of a copper-catalyzed alkynylation involving p-toluenesulfonamide provides high yields of N-Ts-protected propargylamines. The superior activity of copper(II) triflate also allows this three-component alkynylation to incorporate a ketone.

A high-yielding three-component reaction proceeds under mild, solvent-free conditions for access to a wide variety of fully-substituted propargylamines. Inexpensive copper(II) chloride catalyzes the coupling of equimolar amounts of amines, alkynes, and cyclohexanone such that the only byproduct is one equivalent of water.Scheme 1 Versatile KA 2 of cyclohexanone, amines, and alkynes. † Electronic supplementary information (ESI) available: Spectroscopic data and detailed procedures for all compounds are available online free of charge. See