Salts phospholanium

Phospholanium salts have been of considerable interest in the last two decades with respect to the stereochemistry of the interconversion of these salts to phos-pholane oxides and phospholanes. These investigations have centered mainly on understandirtg the steric requirements of phosphorus in a five-membered heterocyclic system with respect to the process of Berry pseudorotation and the existence of pentacoordinated phosphorus intermediates. ... 

Historically, phospholanium salts have been prepared by quaternization in high yield of a selected phospholane with an alkyl halide. Although numerous methods exist for the preparation of the desired phospholanes (recently reviewed ), most of these have major drawbacks, including (1) very critical conditions, such as reaction time, dilution effects, and temperature (2) expensive and/or difficult to manipulate reagents and (3) the necessity of a multistep synthetic sequence giving overall low yields of phospholane. A general example of the latter would be the reaction of a substituted dihalophosphine with a 1,3-diene and hydrolysis to the phospholene oxide, which then can be catalytically reduced to the phospholane oxide and subsequently converted to the phospholane. ... 

The preparation of ethyldiphenylphosphine has been reported and the compound is available commercially. The total working time for preparations A and B is approximately days. Utilization of this procedure has been found to be of general applicability to other phospholanium salts. ... 

Reactions.—Alkaline Hydrolysis. The presence of the oxygen atom as ring member in the oxaphospholanium salts (127) has no effect on the stereochemistry of alkaline hydrolysis, which proceeds with complete retention of configuration at phosphorus to yield the corresponding diastereoisomeric oxides (128). The stereochemical course is the same as that for hydrolysis of the parent phospholanium salts (129), and this... 

A new route to 2-(52) and 3-(51)-(2-aminovinyl)indoles in excellent yield is provided by the reaction of 2- and 3-acylindoles with the carbanions of 1-aminoalkyldiphenylphosphine oxides (50) (Scheme 7).29 The previously established method of diene synthesis using tandem Wittig reactions of the phospholanium salt (53) has been applied to the synthesis of the sex pheromone (54) from the pedal gland of the bontebok (Damaliscus dorcas dorcas) and to various 1,4-diketones (Scheme 8).30... 

The hydrolysis of phospholanium salts based on the five-membered ring generally proceeds considerably faster than that of the corresponding phosphoranium salt based on the six-membered ring. 

Scheme 15.16 Synthesis of mono-, di-, and tridentate phospholane ligands using amines (or NH4CI) and phospholanium salts as key intermediates [67].

The one-pot synthesis of a large family of hi- and tridentate phospholanes represented in Scheme 15.16 employed the air-stable chiral phospholanium chloride salts and primary amines or NH Cl as starting materials. These were transformed into the C2-symmetric dimethylphospholane and diphenylphospholane ligands which reacted with [Rh(COD)2]Bp4 to yield the rhodium complexes [Rh(L)(COD)]Bp4 (L = DMP or DPP bisphospholane ligands) [67]. 

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