The titanium tetrachloride-mediated alkynylation and allylation of a steroidal aldehyde via stannylacetylenes and allylstannanes with high cram selectivity
The reaction of a steroidalaldehyde (1) with stannylacetylenes (2c) in the presence of TiCl4 produces the Cram isomer (3) with high diastereoselectivity.
Molecular hydrogen adds to aliphatic and aromatic alkynylstannanes in the presence of a ruthenium catalyst, pushing the stannyl group to the adjacent carbon atom to give alpha-substituted vinylstannanes. This is the first achievement of hydrogenation of alkynylstannanes, which is applicable also to the deuteration affording precursors for an important class of deuterium-labeled compounds.
Importance of the timing of bond breaking and bond making in acetal templates. Enantiodivergent synthesis of steroidal side chains