Cyclo and Spirozirconation: Synthesis of New Phospholane-Boranes and Polyphosphine-Boranes

Aluminacyclopentanes in the synthesis of 3-substituted phospholanes and α,ω-bisphospholanes

An efficient one-pot process for the synthesis of 3-substituted phospholanes and α,ω-bisphospholanes was developed. The method involves the replacement of aluminium in aluminacyclopentanes, prepared in situ by catalytic cycloalumination of α-olefins and α,ω-diolefins, by phosphorus atoms on treatment with dichlorophosphines (R′PCl₂). Hydrogen peroxide oxidation and treatment with S₈ of the synthesized phospholanes and α,ω-bisphospholanes afforded the corresponding 3-alkyl(aryl)-1-alkyl(phenyl)phospholane 1-oxides, 3-alkyl(aryl)-1-alkyl(phenyl)phospholane 1-sulfides, bisphospholane 1,1'-dioxides, and bisphospholane 1,1'-disulfides in nearly quantitative yields. The complexes LMo(CO)₅ (L = 3-hexyl-1-phenylphospholane, 3-benzyl-1-methylphospholane, 1,2-bis(1-phenylphospholan-3-yl)ethane, and 1,6-bis(1-phenylphospholan-3-yl)hexane were prepared by the reaction of 3-substituted phospholanes and α,ω-bisphospholanes with molybdenum hexacarbonyl. The structure of the complexes was proved by multinuclear ¹H, ¹³C, and ³¹P spectroscopy.

Preparation of enantiomerically pure 2'-substituted 2-diphenylphosphino-1,1'-binaphthyls by reductive cleavage of the carbon-phosphorus bond in a borane complex of 2-diphenylphosphino-2'-diphenylphosphinyl-1,1'-binaphthyl

Reaction of (S)-2'-boranatodiphenylphosphino-2-diphenylphosphinyl-1,1'-binaphthyl (3, borane complex of BINAP monoxide) with an excess of n-butyllithium in THF at -78 degrees C brought about a selective cleavage of the carbon-phosphorus bond between the binaphthyl and diphenylphosphinyl groups to generate the binaphthyllithium 14, the treatment of which with electrophiles MeOD, I(2), and ClSnMe(3) gave, after removal of the borane, the corresponding 2'-substituted 2-diphenylphosphino-1,1'-binaphthyls (E-MOP 9: E = D, I, SnMe(3)), without loss of the enantiomeric purity.