A library of chiral bis-3,4-diazaphospholane ligands was synthesized from an intermediate acyl fluoride bisdiazaphospholane by addition of a primary or secondary amine, yielding carboxamides with varying levels of steric bulk and substitution.  These bisdiazaphospholanes were used in Rh-catalyzed asymmetric hydroformylation (AHF) of six alkene substrates (styrene, vinyl acetate, allyloxy-t-butyldimethylsilane, (E)-1-phenyl-1,3-butadiene, 2,3-dihydrofuran, and 2,5-dihydrofuran) to determine selectivity trends based on steric bulk at the carboxamide position.  Previously inaccessible bisdiazaphospholanes led to remarkable selectivity for 2,3-dihydrofuran (up to 3.8:1 a-isomer:�-isomer ratio and 90% ee for the a-isomer) and 2,5-dihydrofuran (up to <1:30 a-isomer:�-isomer ratio and 95% ee for the �-isomer).  Selected bisdiazaphospholanes were immobilized on Tentagel resin utilizing the same acyl fluoride intermediate and applied to heterogeneous AHF.  Immobilized catalysts maintain high enantioselectivity and can be recycled with minimal Rh leaching.

Supported and solution phase libraries of bisdiazaphospholane ligands for asymmetric hydroformylation

245th National Meeting (2013)

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