Diethyl phosphonite

An improved strategy for the synthesis of P-chiral gluco- and manno-phosphonite boranes 41-43 was developed on the basis of the addition of diethyl phosphonite borane to a glucal-derived aldehyde followed by a cyclization coupled with an ethyl/methyl exchange (Scheme 14) [36]. 

Wasserscheid et al. [116] incorporated guanidinium groups into a Xantphos skeleton via the corresponding bis(diethyl phosphonite), reduction, and final Pd-catalyzed arylation (Scheme 2.33). In the rhodium-catalyzed hydroformylation of... 

An earlier report that diethyl t-butylphosphonite (10) did not undergo an Arbusov reaction, presumably for steric reasons, has been withdrawn since the presumed phosphonite is now shown to be the phosphonate. 

The diethyl ester of phenylphosphonous acid (diethoxyphenyl-phosphine) provides an easy pathway to relatively stable telrakis complexes of zero- and low-valent transition metals.1,2 Anhydrous metal halides serve as the metal source for the complexes, avoiding the necessity of inconvenient starting materials such as nickel carbonyl. The nickel(O) complex is formed by reaction with the phosphonite in ethanol with the addition of sodium tetrahydroborate, relatively stable dihydridoiron(l I) and hydridocobalt(I) complexes are obtained. 

The reaction of a phosphonamidite (79) with a trifluoracetyl ester (80), to give a phosphonite (81), has been shown to be catalysed by 4-dimethylaminopyridine. In contrast to an earlier report where a similar reaction proceeded with retention of configuration at phosphorus, the present system gave an equal amount of the two diastereomers (81). A mechanism is proposed which involves attack of an alkoxide, formed by de-trifluoracetylation of (80), on an equilibrating DMAP-intermediate (82). Another unusual substitution reaction is one between an alkoxyborane (83) and a phosphite (84). The phosphite was prepared in situ from acetylacetone and diethyl phosphorochloridite, and the substitution occurred under very mild conditions and gave high yields of phosphates after oxidation. 

Allyl phosphorodichloridite. 1169 Bis(trimethyIsilyl) phosphonite, 2611 0-0-tert-Butyl diphenyl monoperoxophosphate, 3712 0-0-tert-Butyl di(4-tolyl) monoperoxophosphate, 3763 Diallyl phosphite (Di-2-propenyl phosphonite), 2456 Dibenzyl phosphite, 3658 Dibenzyl phosphorochloridate, 3650 Di(( -( -teri-butyl) ethyl diperoxophosphate, 3374 Dibutyl hydrogen phosphite, 3086 Diethyl ethanephosphonite, 2572 Diethyl 4-nitrophenyl phosphate, 3329 Diethyl 4-nitrophenyl thionophosphate, 3328 Diethyl phosphite, 1733... 

Simple aliphatic aldehydes are also said to yield products which contain the equivalent of 2-3 mol of RCHO per phosphorus atom, some of which have been shown to have an oxyphosphorane structure. (For an introductory account of this fascinating area of phosphorus chemistry, the reader should consult early reviews by Ramirez . ) The phosphite ester obtained from 2-hydroxybenzaldehyde and diethyl chlorophosphite cyclizes with rearrangement to the l,2-benzoxaphosph(V)ole derivative 205 (R = H, R = EtO), and a similar process was observed in the case of phosphites and phosphonites derived from 2-hydroxyacetophenone to give 205 (R = Me) . 

Typical applications of the Michaelis-Arbuzov reaction include the conversion of the 5-deoxy-l,2-0-isopropylidene-3-0-methyl-a-D-xylofuranose derivative 298 into 299 with triethyl phosphite" " or with diethyl ethyl- or butyl-phosphonite to give 300 (R = Et or protection at C ) is also feasible with acetyl or benzoyl moieties . Another example is the conversion of 301 with (MeO)3P into 302 (R = Me) in only 30% yield, but with sodium dibenzyl phosphite into 302 (R = CH2Ph) in 80% yield, and thence via 303 to 304" other similar applications may be noted" ". ... 

Methyl phosphorodichloridite Dimethyl phosphorochloridite Trimethyl phosphite Trimethyl phosphorotrithioite Hexamethylphosphorous triamide Methyl tetramethylphosphorodiamidite Dimethyl dimethylphosphoramidite Methyl diethylphosphoramidochloridite 0-Methyl S.S-diethyl phosphorodithioite Ethylphosphonous acid Ethylphosphonous dichloride Methyl ethylphosphonochloridite Dimethyl ethylphosphonite 0-Methyl S-phenyl ethylphosphonothioite Dibutyl phosphonite ... 

Attack on Unsaturated Carbon.- Bis(trimethylsilyl)phosphonite (14), prepared from ammonium phosphinate and hexamethyldisilazane, adds to o,p-unsaturated ketones (IS) to give high yields of mono- or disubstituted phosphinic acids. Low yields were obtained for enolisable ketones if (14) was prepared in situ from trimethylsilylchloride and triethylamine instead. Diethyl trimethyl-silyl phosphite (16) reacts readily with a,p-unsaturated imines to give solely 1,2-addition products (17), even in the presence of bulky Y-substituents, provided R Ws an aryl group. ... 

An alternative to the Arbuzov route to P-keto phosphonates (40), alkylation of diethyl phosphorochloridite (41) with enolates followed by air-oxidation of the phosphonite, has been evaluated. Although some enolphosphate was formed, the ratios of P-C to P-O products were better than 12.5 1 under optimized conditions, and the products were easy to purify. The reaction is also useful for preparation of a-phosphono esters (42). A full paper has appeared on a new reagent (43) for the determination of optical purities of chiral alcohols or thiols. It is superior to previous reagents because of the large chemical shift difference between the diastereomeric products (44). 

The strategy for the synthesis of phosphinate 54a or 54b involves the activation of the phosphoms atom into the P reactant, followed by successive reactions with a Michael acceptor (ethyl acrylate or diethyl maleate), dibromoethane, and an esterification using triethyl orthoformate. The incorporation of the amino acid group accomplished by nucleophilic substitution of the anion of the diethylaceta-midomalonate yielded the branched phosphinates in 50-77% yield. The final deprotected compounds were obtained in 11-21% yield after acidic deprotection and decarboxylation and they were purified by ion exchange chromatography. Compound 54b was synthesized by alkylation of the phosphonite intermediate with acetamidoacrylic acid, followed by acidic deprotection and ion exchange chromatography purification (Scheme 8). 

Carboranes. A soln. of butylsulfenyl chloride in CCI4 added dropwise at -10 to 0 under argon to a stirred soln. of diethyl (methyl-o-carboranyl)phosphonite in abs. CCI4, and distilled O-ethyl S-butyl (methyl-o-carboranyl)monothiolphos-phonate. Y 90%. A. N. Degtyarev et al., Izvest. 7975, 2369 C. A. 80, 37208. 

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