Novel 10-(substituted)-9-borabicyclo[3.3.2]decane systems (BBDs) are readily prepared from the reaction of stable diazomethanes with B-methoxy-9- borabicyclo[3.3.1]nonane (B-MeO-9-BBN). These reagents are easily resolved in a sequential manner producing both enantiomerically pure forms of the reagents. Reaction of these complexes with Grignard reagents directly provides B-allyl-, allenyl-, or propargyl-10R-BBDs, quantitatively, as stable, isolable compounds in enantiomerically pure form. The corresponding B-crotyl (E and Z) and Z-gamma-OR-allyl reagents are also readily prepared from the enantiomerically pure B-MeO-10R-9-BBDs. The 10-TMS and 10-Ph reagents are specifically tailored for extremely enantioselective additions to aldehydes and ketones, respectively. The specific goals of this project are to develop new chemistry with these robust chiral boranes, including 1) asymmetric "allylboration" with novel 2-boryl-1,3-dienes potentially leading to chiral beta-allenyl carbinols, 2) asymmetric gamma-methoxyallylboration of ketones with a fostriecin application, 3) asymmetric Suzuki-Miyaura coupling and allenylation potentially giving chiral allenes and beta-TMS homopropargylic alcohols with high diastereo- and enantioselectivity, 4) conjugate additions of B-alkynyl-BBDs to enones and N-acylimines, 5) asymmetric propargylboration of ketones, and 6) asymmetric hydroboration of 1,1-disubstituted alkenes to give non-racemic products which are suitable for asymmetric Suzuki-Miyaura alkyl coupling.
With this renewal award, the Organic and Macromolecular Chemistry Program is supporting the research of Dr. John A. Soderquist of the Department of Chemistry at the University of Puerto Rico. Professor Soderquist and his students will study the synthesis and reaction chemistry of compounds containing bonds between carbon and boron. These new "organoborane" reagents are expected to equal or exceed the selectivities reported for other known reagents or processes while offering great versatility as well as ease of preparation, handling and recycling. These studies utilize the rigid, robust bicyclic nature of the organoboranes to create a stable, "enzyme-like" environment for orchestrating highly selective and controlled reactions. This methodology offers promise for a variety of synthetic applications in research and in the pharmaceutical and chemical industries.
