Benzylic phosphine

Using an aldehyde as the key synthon, a reaction, which is termed an anti-Wittig reaction531, has been performed. In this process a benzyl phosphine oxide is treated with butyllithium followed by an aldehyde, to give exclusively an -aikene in high yield (equation 143)532. 

Coughlin and Emrick utilized a benzyl phosphine oxide substituted styrene in olefin metafhesis by (2a) to make... 

Consecutive cyclometallations occur with benzylic phosphines and are controlled by steric and electronic factors ... 

We are not aware of any examples in the literature that describe the photocleavage of a benzylic phosphine. This is consistent with the previously noted poor photoreactivity of the related benzylamines. 

A more easily controlled reaction relies on the use of diamides of the type RCH(NHAc)2 (R = Ph or aryl) with hypophosphorous acid in aqueous acetic acid, when the initial products (Scheme 55) are the [a-(acetylamino)benzyl]phosphinic acid, hydrolysable by mineral acid to the free (a-aminobenzyl)phosphinic acid, and which react further with the same amides in acetic acid to give the bis(a-aminobenzyl)phosphinic acid 378. However phos-phonomethylations of secondary amines proceed satisfactorily to give either type of acid 376 or377 ... 

The formation of this acid has already been described under benzyl-phosphinic acid, p, 115, the white crystalline mass mentioned m that preparation being extracted with potassium hydroxide and precipitated with hydrochloric acid. From hot alcohol it crystallises in shining scales, M.pt. 191° C., readily soluble in hot nitric acid, not very soluble in the usual solvents. It is only a feeble acid, as it does not turn blue htmus red or liberate carbon dioxide from carbonates. The potassium and silver salts are known, the latter reacting with methyl iodide to form the methyl ester, consisting of bushy, silky prisms, M.pt. 75° C. Nitration produces 4 4 -dinitrodibenzylphosphinie acid, forming colourless needles, M.pt. 225° to 226° C. ... 

The reaction of the dialdehyde, obtained by a double ozonolysis of 118, with dibenzyl aspartate afforded the cyclic benzyl phosphinate 119. A pallado-catalyzed hydrogenolysis produced 4-azaphosphinane 107 in 85% yield (Scheme 24). 

CaHaOtP Bis-[a-acetoxy-benzyl]-phosphin s tire-athylester 7, 233. Bi8-[a-benzoyloiQr-isapropy]]-phoaphni< a ure 9,147. 

Lithiation at C2 can also be the starting point for 2-arylatioii or vinylation. The lithiated indoles can be converted to stannanes or zinc reagents which can undergo Pd-catalysed coupling with aryl, vinyl, benzyl and allyl halides or sulfonates. The mechanism of the coupling reaction involves formation of a disubstituted palladium intermediate by a combination of ligand exchange and oxidative addition. Phosphine catalysts and salts are often important reaction components. 

Heteroleptic complexes of uranium can be stabilized by the presence of the ancillary ligands however, the chemistry is dominated by methyl and benzyl ligands. Examples of these materials include UR4(dmpe) (R = alkyl, benzyl) and U(benzyl)4MgCl2. The former compounds coordinate "soft" chelating phosphine ligands, a rarity for the hard U(IV) atom. 

Phosphinamides are stable to catalytic hydrogenation, used to cleave benzyl-derived protective groups, and to hydrazine. The rate of hydrolysis of phosphin-... 

C. Reactions of Phosphoric and Phosphinic Acid Derivatives.—The optically active phosphinate ester (90) has been shown to react with benzyl Grignard reagents or lithium anilide with inversion of configuration. Oxidation of... 

Lord and Pawliszyn" developed a related technique called in-tube SPME in which analytes partition into a polymer coated on the inside of a fused-silica capillary. In automated SPME/HPLC the sample is injected directly into the SPME tube and the analyte is selectively eluted with either the mobile phase or a desorption solution of choice. A mixture of six phenylurea pesticides and eight carbamate pesticides was analyzed using this technique. Lee etal. utilized a novel technique of diazomethane gas-phase methylation post-SPE for the determination of acidic herbicides in water, and Nilsson et al. used SPME post-derivatization to extract benzyl ester herbicides. The successful analysis of volatile analytes indicates a potential for the analysis of fumigant pesticides such as formaldehyde, methyl bromide and phosphine. 

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