Stereocontrolled Copper Iodide Catalyzed Phosphorus-Carbon Bond Formation: An Efficient Synthesis of Scalemic Tertiary Phosphineboranes

Abstract

A mild and efficient protocol for P-C bond formation was developed with sub-stoichiometric amounts of copper iodide as a catalyst. A series of sterically and electronically divergent phosphineboranes were subjected to coupling reactions and the corresponding products were obtained in high yields with retention of configuration. The reaction proceeded under non-basic conditions thus avoiding base-catalyzed racemization.

Asymmetric Electrophilic Reactions in Phosphorus Chemistry

“…The reduction of the P=O bond with BH3 is possible due to the intramolecular complexation of P=O•B coordinated by α-or β-hydroxy groups present in the phosphine oxide structure. The conversion of hydroxyalkylphosphine oxides to hydroxyalkylphosphine boranes were obtained with a full inversion of the configuration at phosphorus [164,[166][167][168][169]. It was found that the P-alkylation reaction proceeds with good yield and high enantiospecificity (ee > 95%) with various alkyl halides.…”

“…Chiral phosphine boranes obtained from adamantylphosphinates are of interest as synthetic blocks (Equations (117) and (118)) [138]. (116) (117) (118) An alternative method for the synthesis of P-stereogenic adamantyl phosphinates is based on the introduction of a hydroxymethyl group into phosphinates to control the stereoselectivity of the subsequent reduction by borane-THF complex [167][168][169]. The reaction of adamantylphosphinates with formaldehyde led to the formation of optically pure hydroxymethylphosphinates (Equation (119)).…”

“…The synthesis of functionalized tertiary phosphine boranes was developed using a chemodivergent approach from readily available (hydroxymethyl)phosphine boranes under mild conditions and high regioselectivity with the formation of an exclusively O-alkylation product. The reaction proceeded with a moderate or very good yields and high enantiospecificity (es> 95%) (Equation (121)) [169]. (121) The phospha-Mannich reaction is the addition of phosphites to imines leading to the formation of aminophosphonates possessing diverse biological activity [170][171][172][173].…”

Recent Advances in Metal-Catalyzed C–P Bond Formation

“…When PHPh(t-Bu)(BH 3 ) of 99% ee was used, the reaction proceeded with retention of configuration at phosphorus (Scheme 36); other chiral phosphine-boranes behaved similarly [58]. …”

Developing a new phosphorus-carbon bond synthesis

“…Cu-catalysed reaction of ethyl diazoacetate and enantiopure secondary phosphine borane produces enantiopure tertiary phosphine-borane complex in good yields. [185] P-chiral phosphine and diphosphine species can also be synthesised via Pt-and Ru-catalysed enantioselective coupling of racemic secondary phosphines with alkyl bromides and chlorides respectively (Scheme 1.51 and 1.52). [186][187] Scheme 1.51 Pt-catalysed asymmetric alkylation of secondary phosphines.…”