Phosphoric acid derivatives reductions

Stereoselective l.4-reduction oi the 1.3-butadiene system to olefin 57 lakes place tinder the conditions of the Birch reduction. Intramolecular protonation of the intermediate carbanion at the 18-position to give 57 occurs with high selectivity syn to the hydroxymethy-iene group Conversion into phosphoric acid derivative 58 and cleavage of the phosphoric acid amide group under (he conditions of the Bcnkeser reduction provides compound 5921 Fluonde ion causes the release of free p-amyrin (1) in a final step I Li, NH3(iyTllF (1/1.75), -78 C 93%. 

The first example of highly enantioselective reduction of ketones (320) with catecholborane (321) as a reducing agent, catalysed by a chiral phosphoric acid derivative (323), gave chiral secondary alcohols (322) with high enantioselectivities (Scheme 84). ... 

The largest-volume phosphoms compounds are the phosphoric acids and phosphates (qv), ie, the oxide derivatives of phosphoms ia the + 5 oxidation state. With the exception of the phosphoric acid anhydride, P O q, and the phosphate esters, these materials are discussed elsewhere (see Phosphoric acids and phosphates). An overview of phosphoms compounds other than the phosphoric acids and phosphates is given herein. These compounds constitute a large variety of phosphoms compounds that are either nonoxide derivatives or derivatives of phosphoms ia oxidation states lower than + 5. These phosphoms compounds are manufactured only from elemental phosphoms (qv) obtained by reduction of naturally occurring phosphate rock (calcium phosphate). 

Ethylamines. Mono-, di-, and triethylamines, produced by catalytic reaction of ethanol with ammonia (330), are a significant outlet for ethanol. The vapor-phase continuous process takes place at 1.38 MPa (13.6 atm) and 150—220°C over a nickel catalyst supported on alumina, siUca, or sihca—alumina. In this reductive amination under a hydrogen atmosphere, the ratio of the mono-, di-, and triethylamine product can be controlled by recycling the unwanted products. Other catalysts used include phosphoric acid and derivatives, copper and iron chlorides, sulfates, and oxides in the presence of acids or alkaline salts (331). Piperidine can be ethylated with ethanol in the presence of Raney nickel catalyst at 200°C and 10.3 MPa (102 atm), to give W-ethylpiperidine [766-09-6] (332). 

D-(l-2H)Glucopyranose was prepared (170) by direct reduction of D-glu-cono-1,5-lactone, in deuterium oxide solution, with sodium amalgam in the presence of phosphoric acid-rf3, or, alternatively, by reduction of the lactone tetrahydropyranyl derivative with sodium borodeuteride in tetrahydrofuran (171). 

The total synthesis of pavinane alkaloid platycerine (89) (Scheme 14) has been accomplished successfully (26) via 1-benzylisoquinoline derivative 91 obtained from Reissert intermediate 90. Quatemarization of 91 with methyl iodide followed by lithium aluminum hydride reduction supplied 1,2-dihydroisoquinoline 92, which on treatment with a 7 5 mixture of formic acid and phosphorous acid gave ( )-platycerine (89) in 60-70% yield. 

In other developments, Lecat and Devaud ° have proposed an electrochemical reduction (Scheme 4) to recover triphenylphosphine from triphenylphosphine oxide produced, for example, in the Wittig reaction. Yields of up to 86% were obtained. Engel and Chakrabarty have reduced phosphoric and phosphonic chlorides to the corresponding monobasic phosphorous and phosphonous acid derivatives (equations 23 and 24), using NaBH4 in refluxing dioxane. Triphenylphosphine oxide is reportedly reduced to triphenylphosphine in 75% yield by the electron-transfer system Smh-THF-HMPA, at 65 °C. 

The important functional groups present in monosaccharides are hydroxyl and carbonyl groups. The hydroxyl group forms esters, usually with phosphoric acid or is replaced by a hydrogen or amino group. The carbonyl group undergoes reduction or oxidation to produce number of derived monosaccharides. 

An even more facile synthesis of XX was achieved by Mondon (10) using the amide derived from 3,4-dimethoxyphenyIethylamine (XXVI) and 2-ketocyclohexaneacetic acid (XXVII). The amide XXVIII is prepared simply by heating the ethylene ketal of XXVII with XXVI it cyclizes on warming in phosphoric acid to a lactam (XXIX) isomeric with Belleau s. Lithium aluminum hydride reduction gives the same racemic base (XX). The intermediate lactam XXX can be prepared in... 

Soon after these initial reports, the groups of Antilla [92] and You [93] indepen dently applied the chiral phosphoric acid catalysis to the enantioselective hydro genation of a imino esters. The method provides an alternative route to the enantioselective synthesis of a amino esters. Antilla and coworkers employed a new type of axially chiral phosphoric acid (9) derived from VAPOL originally developed by his research group (Scheme 3.42), whereas lg was used in You s case. In both cases, excellent enantioselectivities were achieved. You and coworkers further applied the method to the enantioselective reduction of a imino esters having an alkynyl substituent at the a position (Scheme 3.43) [94]. Both alkyne and imine moieties were reduced under transfer hydrogenation conditions with an excess amount of... 

Synthesis of Phosphoric Acids and Their Derivatives. - A series of monoalkyl and dialkyl phosphorus acid chiral esters have been synthesised for use as carriers for the transport of aromatic amino acids through supported liquid membranes. The compounds acted as effective carriers but enantio-separation was at best moderate. A range of phosphono- and phosphoro-fluoridates have been prepared by treatment of the corresponding thio- or seleno- phosphorus acids with aqueous silver fluoride at room temperature (Scheme 1). In some cases oxidation rather than fluorination occurred. Stereospecifically deuterium-labelled allylic isoprenoid diphosphates, e.g. (1), have been synthesised from the corresponding deuterium-labelled aldehyde by asymmetric reduction, phosphorylation and Sn2 displacement with pyrophosphate (Scheme 2). ... 

Reduction of ArCOOH and derivatives.2 Aryl carboxylic acids can be reduced to ArO-UOH by Sml2 (excess) in the presence of an acid, particularly phosphoric acid (85%). In contrast pyridinccarboxylic acids are reduced to the corresponding methylpyridine in 43-48% yield. Benzoic anhydride and benzoyl chloride are also reduced to benzyl alcohol, but in lower yield. Benzonitrilc is reduced under the same conditions to benzylamine in 99% yield. This behavior is characteristic for aryl nitriles. 

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