Intramolecular cycloaddition reactions of oximes with vinyl sulfones

Highly Regioselective and Stereoselective Hydrostannylation of (Z)-2-Ethoxycarbonyl-1,3-Enynes Leading to (1E,3E)-2-Ethoxycarbonyl-3-Stannyl-1,3-Dienes

The Stille coupling of (E)-α-stannyl-α,β-unsaturated esters with alkynyl bromides in DMF in the presence of Pd(PPh3)4 and CuI gave (Z)-2-ethoxycarbonyl-1,3-enynes in good yields. The latter underwent the palladium-catalysed hydrostannylation with tributyltin hydride in THF at room temperature to afford (1E,3E)-2-ethoxycarbonyl-3- stannyl-1,3-dienes in good yields with high regio- and stereoselectivities.

Use of sulfur fragments for the synthesis of nitrogen heterocycles

This contribution contains a representative sampling from the Padwa laboratory of the conjugate addition of oximes with 2,3-bis(phenylsulfonyl)-1,3-butadiene followed by a subsequent dipolar cycloaddition cascade to produce a variety of alkaloids. The resulting cycloadducts are cleaved reductively to provide azapolycyclic scaffolds with strategically placed functionality for further manipulation of the target compounds.

Stereoselective Synthesis of Difunctionalised 1,3-dienes Containing Silicon and Sulfur via Palladium Catalysed Cross-Coupling Reactions

Hydromagnesiation of alkynylsilanes 1 in diethyl ether gave ( Z)-α-silylvinyl Grignard reagents 2, which underwent a cross-coupling reaction with ( E)-α-iodovinyl sulfides 3 in the presence of Pd(PPh3)4 as catalyst to afford stereoselectively ( Z,Z)-2-silyl-3-arylsulfanyl-substituted 1,3-dienes 4 in good yields.