A Novel Type of Chiral Triangulane-Based Diphosphane Ligands for Transition Metals

A new original strategy for the synthesis of axially and helically chiral bidentate diphosphane ligands featuring a rigid triangulanyl backbone has been elaborated and executed for several representative enantiomerically pure ligands. Thus,(1R,3S,4S)-1,4-bis[(diphenylphosphanyl)methyl]spiro[2.2]pentane [(1R,3S,4S)-24·(BH3)2], [(1R,3R,4S)-4-(diphenylphosphanyl)methylspiro[2.2]pentan-1-yl]diphenylphosphane [(1R,3R,4S)-27·(BH3)2], [(1R,3R,4S,5R)-5-(diphenylphosphanyl)methyldispiro[2.0.2.1]heptan-1-yl]diphenylphosphane [(1R,3R,4S,5R)-30·(BH3)2], (1S,3S,4S)-1,4-bis(diphenylphosphanyl)spiropentane [(1R,3S,4S)-35·(BH3)2], (1S,3S,4S)-1,4-bis(diphenylphosphanyl)spiropentane [(1S,3S,4S)-35·(BH3)2], (1S,3S,4S)-1,4-bis(diphenylphosphanyl)spiropentane [(1R,3R,4S)-35·(BH3)2], and (1R,3R,4R,5R)-1,5-bis(diphenylphosphanyl)dispiro[2.0.2.1]heptane [(1R,3R,4R,5R)-36·(BH3)2] with a spiropentyl and a dispiro[2.0.2.1]heptyl moiety, respectively, have been prepared as bishydroborane complexes applying repetitively the same set of standard synthetic operations, starting from [(1S,3R)-4-methylenespiropent-1-yl]methyl acetate [(1S,3R)-7], (4,4-dibromospiropent-1-yl)methanols [(1S,3R)-8 and (1R,3S)-8] and (dibromodispiro[2.0.2.1]heptyl)methanols (1R,3S,4R)-9, (1S,3R,4S)-9 and (1S,3R,4R)-9 in 4–7 steps. The relative configurations of all important intermediates as well as the absolute configurations of the key intermediates and most final products were established by X-ray crystal structure analyses.