Divergent Synthetic Access to - and -Stereodefined All-Carbon-Substituted Olefin Scaffolds: Application to Parallel Synthesis of ()- and ()-Tamoxifens.

A highly substrate-general synthesis of all-carbon-substituted - and -stereodefined olefins is performed. The method comprises two sets of parallel and stereocomplementary preparations of ()- and ()-α,β-unsaturated esters involving two robust and distinctive reactions: 1) stereocomplementary enol tosylations using readily available TsCl/diamine/(LiCl) base reagents, and 2) stereoretentive Negishi cross-coupling using the catalysts [Pd(dppe)Cl] (for ) and [Pd(dppb)Cl] (for ). The present parallel approach is categorized as both type I (convergent approach: 16 examples, 56-87 % yield) and type II (divergent approach: 18 examples, 70-95 % yield).

Synthesis and Alkali-Metal-Ion Complexation of P-Stereogenic Diphosphacrowns.

Phosphine is conformationally stable because of the high inversion energy barrier of the phosphorus atom, which allows the phosphorus atom to become a chiral center. Thus, enantiopure P-stereogenic 12-, 15-, 18-, and 21-membered aliphatic phosphines "diphosphacrowns" were synthesized from secondary P-stereogenic bisphosphine as a chiral building block. Their complexation behaviors with alkali metal ions are investigated in comparison with benzo-18-diphosphacrown-6 and benzo-18-crown-6.