Hydroxy nitriles Nickel

The zwitterion (6) can react with protic solvents to produce a variety of products. Reaction with water yields a transient hydroperoxy alcohol (10) that can dehydrate to a carboxyUc acid or spHt out H2O2 to form a carbonyl compound (aldehyde or ketone, R2CO). In alcohoHc media, the product is an isolable hydroperoxy ether (11) that can be hydrolyzed or reduced (with (CH O) or (CH2)2S) to a carbonyl compound. Reductive amination of (11) over Raney nickel produces amides and amines (64). Reaction of the zwitterion with a carboxyUc acid to form a hydroperoxy ester (12) is commercially important because it can be oxidized to other acids, RCOOH and R COOH. Reaction of zwitterion with HCN produces a-hydroxy nitriles that can be hydrolyzed to a-hydroxy carboxyUc acids. Carboxylates are obtained with H2O2/OH (65). The zwitterion can be reduced during the course of the reaction by tetracyanoethylene to produce its epoxide (66). 

Hydroxylamines and derivatives Borane-Tetrahydrofuran, 42 Dimethylphenylsilane, 123 Hydroxy nitriles (see also Cyanohydrins) Nickel, 197 Hydroxy selenides... 

Talaromycin B is a spiro-acetal produced by the fungus Talaromyces stipitatus, the toxicity of which may be due to its ability to block outward potassium fluxes. In an elegant synthesis, the requisite open-chain polyol with hydroxy groups in the y-and y -positions was assembled from nitrile oxide and olefin building blocks 50 and 51, both of which carry a f>w(hydroxyethyl) moiety protected as a cyclohexanone acetal (284). Hydrogenolysis of the N O bond of isoxazoline 52 using Raney nickel, followed by treatment with aqueous acid, gave the spiroketal 53, which was further transformed into racemic talaromycin B (54) (Scheme 6.54) (284). 

Isoxazolines can be transformed into a,p-enones by several methods from the initial aldol product. This strategy was applied by Barco et al. (285) toward the synthesis of ( )-pyrenophorin (98), a macrocychc fow(enone-lactone) with antifungal properties. The hydroxy group was introduced from the nitrile oxide component (95), while the carboxy function was derived from the acrylate dipo-larophile. Thus, cycloaddition of the optically active nitropentyl acetate 94 to methyl acrylate 95 afforded isoxazoline 96 as a mixture of optically active diastereomers. Reductive hydrolysis using Raney nickel/acetic acid gave p-hydro-xyketone (97), which was subsequently utilized for the synthesis of (—)-pyreno-phorin (98) (Scheme 6.63) (285). 

Bis-[2-hydro y-athyl]-(6-aniino-hcxyl)-amiiL Ein Gemisch von 20 g (0,1 Mol) 6-(Bis-[2-hydroxy-athyl]-amino)-hexansaure-nitril, 3g Raney-Nickel, 5 ml 10%ige athanolische Ammoniak-Losung und 50 ml Athanol wird bei 3,5 bar und 20c hydriert. Die Wasserstoff-Aufnahme ist nach 5 Stdn. beendet. Der Katalysator wird abgctrcnnt, das Losungsmittel verdampft und dcr Riickstand i.Vak. destilliert Ausbeute 14 g (75% d.Th.) Kp(, .v 155—IST"1 n3,6 = 1,4885. 

A very efficient chain extension consists of the reaction with the lithium salt of t-hutyl acetate. The 5-hydroxy-)S-keto-ester is reduced with high selectivity, using sodium horohydride/diethyhnethoxyhorane, to the sy/i-l,3-diol with a diastereomeric ratio of 100 1. The acetonide is a well-crystaUisable substance its purification in a single recrystaUisation step results in a diastereomeric ratio of 350 1. Reduction ofthe nitrile function with molybdenum-doped Raney nickel produces the side-chain. 

Figure 4.27. Effect of plasticizer on the indentation of crosslinked nitrile rubber 5°C/min, no plasticizer (medium dashed line) lOphr coumarone indene resin (solid line) lOphr hydrocarbon resin (long dashed line) lOphr hydroxy resin (short dashed line) [from Brazier and Nickel (1978) reprinted with permission of Elsevier].

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