System under mildly reducing conditions

The attachment of the strongly electronegative phosphinyl (P—O) group to an imine, usually via reaction of an oxime with a chlorophosphine, also gives highly electrophilic imines which are reduced by NaBFWTHF and various modified borohydride and LAH derivatives " under mild conditions. The product A-phosphinylamines are protected forms of primary amines since removal of the phosphorus substituent is accomplished under mild acidic conditions. Entries 12 and 13 (Table 16) present representative reductions and illustrate (entry 13) that highly diastereoselective reductions of cyclic systems to axial amine derivatives are accomplished with LiBHBu s. Enantioselective reductions of A-diphenylphosphinyl imines to optically active amine derivatives have also been reported (Chapter 1,7, this volume). ... 

It is clear that the instability of FMC 55626 greatly reduces its field performance. The search for a solution to this problem became our prime concern. The observed gas evolution under mildly basic conditions suggests that the decarboxylation of FMC 55626 is a facile process. It was, therefore, desirable to remove the "lactone" carbonyl group from the isoxazolidinedione system 6 to... 

Iodosylbenzoic acid (85) is also a convenient recyclable hypervalent iodine oxidant for the synthesis of a-iodo ketones by oxidative iodination of ketones [88], Various ketones and p-dicarbonyl compounds can be iodinated by this reagent system under mild conditions to afford the respective a-iodo substituted carbonyl compounds in excellent yields. The final products of iodination are conveniently separated from by-products by simple treatment with anionic exchange resin Amberlite IRA 900 HCOs" and are isolated with good purity after evaporation of the solvent. The reduced form of the hypervalent iodine oxidant, 3-iodobenzoic acid (59), can be recovered in 91-95% yield from the Amberlite resin by treatment with aqueous hydrochloric acid followed by extraction with ethyl acetate [88]. 

Aliphatic polyesters were also synthesized via an enzymatic polymerization of dicarboxyiic acids and glycols in a solvent-free system [69, 70]. The lipase from Candida antarctica (lipase CA) provided an efficient catalysis of the polymerization under mild reaction conditions, despite the presence of a heterogeneous mixture of the monomers and catalyst. The ahphatic chain length of the monomers had a major effect on both the polymer yield and molecular weight typically, a molecular weight in excess of 1 x Da was obtained when the reaction was conducted under reduced pressure. However, the addition of a small amount of adjuvant proved effective for polymer production when both monomers were solid at the reaction temperature [71]. 

C in the presence of CO, H2O, base and a phase transfer catalyst (particularly 18-crown-6, 87 turnovers). Aromatic nitro compounds are reduced under mild conditions in a genuine bimetallic phase transfer catalysed reaction (reaction 7) , or by a (PtClj (PPhs )2 ]/SnCli,/Et3N system under more forcing conditions. ... 

Tetrabutylammonium iodide in trifluoroacetic anhydride is an effective reducing reagent [dS] This system can be used for direct reduction of arenesulfonic acids to the corresponding thiols or disulfides m moderate yields under mild conditions (equation 18) Alkanesulfonic acids are reduced by this system to disulfides with 30-57% yields [dfi]... 

Hydroxylamines ordinarily do not accumulate in the reduction of aromatic nitro compounds for, with some exceptions, most systems in competition will reduce the hydroxylamine function preferentially. Nonetheless, systems have been found that afford the intermediate aromatic hydroxylamine in excellent yield. With hydrogen gas as a reductant and platinum-on-carbon or -on-alumina and about I wt % of DMSO based on nitro compound as a modifier, aromatic hydroxylamines can be formed in 90% yield under mild conditions. The reduction slows markedly after absorption of the second mole of hydrogen and should be stopped at this stage (80). 

TS-1-catalyzed processes are advantageous from the environmental point of view as the oxidant is aqueous hydrogen peroxide, which turns into water, and the reactions are operated in liquid phase under mild conditions, showing very high selectivity and yields, thus reducing problems and the costs of by-product treatments. Confinement of the metal species in the well-defined MFl pore system endows TS-1 with shape selectivity properties analogous to enzymes. For these features the application of the terms mineral enzyme or zeozyme to TS-1 is appropriate [42]. 

A similar polymer-stabilized colloidal system is described by James and coworkers [66]. Rhodium colloids are obtained by reducing RhCls, 3H2O with ethanol in the presence of PVP. The monophasic hydrogenation of various substrates such as benzyl acetone and 4-propylphenol and benzene derivatives was performed under mild conditions (25 °C and 1 bar H2). The nanoparticles are poorly characterized and benzyl acetone is reduced with 50 TTO in 43 h. 

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