Primary alkyl bromides, phosphonate

Although it might be expected that reactions which employed triarylmethyl halides would occur very readily, such reactions are rendered potentially more complex by the known nature of the halides and their propensity for involvement in free radical reactions. Whereas normal alkylation proceeds between sodium diethyl phosphite and diphenyl-methyl halides, success, or otherwise, in the use of the triphenylmethyl halides depends to some extent on the individual halide and on the metal in the phosphite salt. Thus, in an early study (in 1939), Arbuzov found that in reactions between silver dialkyl phosphites and triphenylmethyl bromide, dialkyl triphenylmethylphosphonates were indeed formed, but the use of the corresponding alkyl chloride provided the phosphite triester instead (metal dialkyl phosphites possess ambident anions ). A later study confirmed the behaviour of the silver salts towards the chloride, but also showed that, whereas dialkyl phophites with primary alkyl groups yielded phosphonic diesters (as had already been found), those with secondary alkyl groups afforded phosphite triesters moreover, the presence and nature of aromatic substituents were also able to control the course of the reaction. Reactions which involve triarylmethyl halides and sodium dialkyl phosphites may well be of a free radical nature since repeated studies have demonstrated the forma-... 

Reaction with Primary Alkyl Bromides, Iodides, or Triflates. Treatment of the sodium or potassium salt of phenylsulfonylfluoromethylphosphonate with primary alkyl bromides (eq 6), iodides, or triflates (eq 7) affords (Q -fluoro-Q -phenylsulfonylalkyl)phosphonates in moderate to good yields, which could be converted to the corresponding (Q -fluoroalkyl)phosphonates via Na(Hg)-mediated desulfonation (eq7).l ... 

The addition of Lithium Bromide and Lil was shown to enhance the rate of organozinc formation from primary alkyl chlorides, sulfonates, and phosphonates, and zinc dust. Beneficial effects of Lil addition have also been reported for Heck-type coupling reactions and in conjugate addition to chiral vinyl sulfoximines. ... 

The sulfone moiety was reductively removed and the TBS ether was cleaved chemoselectively in the presence of a TPS ether to afford a primary alcohol (Scheme 13). The alcohol was transformed into the corresponding bromide that served as alkylating agent for the deprotonated ethyl 2-(di-ethylphosphono)propionate. Bromination and phosphonate alkylation were performed in a one-pot procedure [33]. The TPS protecting group was removed and the alcohol was then oxidized to afford the aldehyde 68 [42]. An intramolecular HWE reaction under Masamune-Roush conditions provided a macrocycle as a mixture of double bond isomers [43]. The ElZ isomers were separated after the reduction of the a, -unsaturated ester to the allylic alcohol 84. Deprotection of the tertiary alcohol and protection of the prima-... 

Reactions with —OH Groups and Epoxides.—The formation of A -l,2-oxaphos-pholen derivatives from propargylic alcohols and phosphorus trichloride has been studied in detail. Intermediate phosphites (24) and allenic phosphonates (25) are described, and the A -l,2-oxaphosphoIen is produced in the final stage, as shown. Improved conditions have been outlined for the preparation of allylic bromides (26) from allylic alcohols and phosphorus tribromide. Related reactions of primary alcohols with the complex of phosphorus trichloride and DMF lead to the chloride (27) 22 addition of zinc bromide to the reaction results in the formation of alkyl bromides, but an attempt to extend this exchange to the preparation of cyanides was not successful. ... 

Primary, secondary and tertiary alkyl chlorides, bromides or iodides all undergo reaction (vinyl halides and alkyl fluorides do not), as do cycloalkyP" " and benzyP " halides. Apart from the compilation of examples by Kinnear and Perren ", other examples are spread very widely and rather thinly throughout the literature. Some isomerization is to be found when using certain alkyl halides for example, -propyl and -butyl halides afford the isopropyl- and (l-methylpropyl)-phosphonic dichlorides, and isobutyl chloride yields r r/-butylphosphonic dichloride ". Whilst Me3SiCH2Cl affords the expected phosphonic dichloride, neopentyl chloride yields (l,l-dimethylpropyl)phosphonic dichloride ". 1,5-Dichloropentane reacts but affords only (4-chloro-l-methylbutyl)phosphonic dichloride " ... 

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