Jose L. Mascarenas

Palladium-catalysed coupling of vinyl triflates with enynes and its application to the synthesis of 1α-25-dihydroxyvitamin D3

Abstract We describe a general approach, based on the palladium-catalysed coupling of enynes with vinyl triflates, for the construction of dienynes related to vitamin D metabolites and analogues. As an application of this method, an efficient convergent synthesis of 1α,25-dihydroxyvitamin D 3 starting from the Inhoffen-Lythgoe diol ( 6a ) and natural carvones has been carried out (11 steps, 28% overall yield from 6a ). This strategy allows labelling of the side chain in the final steps of the synthesis

Ruthenium-Catalyzed (2 + 2) Intramolecular Cycloaddition of Allenenes

We report a ruthenium-catalyzed (2 + 2) intramolecular cycloaddition of allenes and alkenes. We have found that the use of the ruthenium complex RuH(2)Cl(2)(P(i)Pr(3))(2), which has previously gone unnoticed in catalytic applications, is crucial for the observed reactivity. The reaction proceeds under mild conditions and is fully diastereoselective, providing a practical entry to a variety of bicyclo[3.2.0]heptane skeletons featuring cyclobutane rings.

Palladium-catalyzed conjugate addition of terminal alkynes to enones.

A practical protocol for the hydroalkynylation of enones using Pd catalysis is reported. The reaction proceeds efficiently with a variety of alkynes as well as with several cyclic and acyclic enones, providing synthetically relevant β-alkynyl ketones in good to excellent yields.