Salicylaldehyde, reduction

Amino acids were protected by reductive alkylation with salicylaldehyde (NaBH4, KOH, aq. EtOH). The amine is released by treatment with CF3SO3H (TFA, EDT, PhSMe, 2 h, >75% yield). ... 

Reaction of the potassium salt of salicylaldehyde with chlo-roacetone affords first the corresponding phenolic ether aldol cyclization of the aldehyde with the ketonic side chain affords the benzofuran (1). Reduction of the carbonyl group by means of the Wolf-Kischner reaction affords 2-ethyl-benzofuran. Friedel-Crafts acylation with anisoyl chloride proceeds on the remaining unsubstituted position on the furan ring (2). The methyl ether is then cleaved by means of pyridine hydrochloride (3). lodina-tion of the phenol is accomplished by means of an alkaline solution of iodine and potassium iodide. There is thus obtained benziodarone (4)... 

Another CNS active agent in this structural class is the tranquilizer-antidepressant caroxazone (52). Its published synthesis begins by reductive aminatiwi of salicylaldehyde and glycinamide to give The synthesis is completed by reaction with phosgene and sodium bicarbonate. ... 

Method B involves the preparation of precursor of 2-alkyl-l-benzo-pyrylium salts, as shown in Scheme ll.50 2-Alkylbenzopyrylium salts have been prepared by condensation of salicylaldehyde with appropriate ketone in acetic acid or by alkylation or reduction of coumarin or chromone derivatives. Reaction of 2-alkylbenzopyrylium salts with salicylaldehyde gives directly a spirodibenzopyran or 2-vinynologue benzopyrylium salt 17 which then can be converted into the spirodibenzopyran by piperidine or pyridine. 

The electrochemical behavior of an aqueous/ethanol solution of [Ir(sat)2]Cl, satH = salicylaldehyde thiosemicarbazone (235), has been studied on mercury. A two-electron, ligand-based reduction at —1.09 V vs. SCE (independent of pH) is observed at fast scan rates.406... 

In the presence of a catalytic amount of the optically active Mn(III)-saIen complexes 23 and 24, the enantioselective epoxidation of unfunctionalized olefins with the combined use of molecular oxygen and pivaMdehyde was demonstrated. This report revealed that the tert-butyl group on the C3 position of salicylaldehyde in the chiral ligand was essential to realize a high enantioselection, and that pivalaldehyde was the most effective reductant for both the enantioselectivity and chemical yield. It should be noted that the sence of enantioselectivity to form the epoxide from 1,2-... 

Reduction of the carboxylic acid group passes through the intermediate aldehyde. For a number of examples in the heterocyclic series, the aldehyde becomes a major product because it is trapped as the hydrated vfc.-diol form. Examples include imidazole-2-caiboxylic acid [139], thiazole-2-carboxylic acid [140] and pyridine-4-carboxylic acid [141] reduced in dilute aqueous acid solution. Reduction of imidazole-4-carboxylic acid proceeds to the primary alcohol stage, the aldehyde intermediate is not isolated. Addition of boric acid and sodium sulphite to the electrolyte may allow the aldehyde intermediate to be trapped as a non-reducible complex, Salicylaldehyde had been obtained on a pilot plant scale in this way by... 

Numerous methods for the synthesis of salicyl alcohol exist. These involve the reduction of salicylaldehyde or of salicylic acid and its derivatives. The alcohol can be prepared in almost theoretical yield by the reduction of salicylaldehyde with sodium amalgam, sodium borohydride, or lithium aluminum hydride by catalytic hydrogenation over platinum black or Raney nickel or by hydrogenation over platinum and ferrous chloride in alcohol. The electrolytic reduction of salicylaldehyde in sodium bicarbonate solution at a mercury cathode with carbon dioxide passed into the mixture also yields saligenin. It is formed by the electrolytic reduction at lead electrodes of salicylic acids in aqueous alcoholic solution or sodium salicylate in the presence of boric acid and sodium sulfate. Salicylamide in aqueous alcohol solution acidified with acetic acid is reduced to salicyl alcohol by sodium amalgam in 63% yield. Salicyl alcohol forms along with -hydroxybenzyl alcohol by the action of formaldehyde on phenol in the presence of sodium hydroxide or calcium oxide. High yields of salicyl alcohol from phenol and formaldehyde in the presence of a molar equivalent of ether additives have been reported (60). Phenyl metaborate prepared from phenol and boric acid yields salicyl alcohol after treatment with formaldehyde and hydrolysis (61). 

Ruoho and Rong have descnbed a shorter route to salmeterol (Scheme 4). Friedel-Crafts acylation of salicylaldehyde (16) with bromoacetyl bromide in the presence of aluminum chloride gave the acetophenone 17. Alkylation of amine 18 with bromoacetyl 17 in refluxing acetonitrile gave the ketone 19. Reduction of 19 with sodium borohydride in methanol followed by catalytic hydrogenolysis of the benzyl group over 10% Pd/C gave salmeterol (2). 

Kinetics of the reaction of certain Mo02L complexes (L = S-containing salicylaldehyde Schiff base) with PEtPh2 also show the reactions to be first order in complex and in phosphine,145-147,168 The rate constants depend upon the substituent on the aromatic (salicylaldehyde derived) ring and correlate with reduction potentials of the complexes.145... 

Salicylaldehyde Salicylic acid (India) Past pilot-plant Reduction of functional group... 

Another synthetic use of the M-P-V reaction has been exploited in the synthesis of new alkoxide derivatives.247,248 Hence, 2-hydroxybenzaldehyde (salicylaldehyde) will react with isoproxides of titanium and zirconium to initially displace isopropyl alcohol and give mixed derivatives which on heating undergo reduction of the aldehyde function with elimination of acetone. The stoichiometry of the overall reaction can be represented as shown in equation (66).248... 

Saccharin, 2-methyl-reduction, 6, 152 Saccharin, 6-nitro-reduction, 6, 154 Saccharin, thio-hydrolysis, 6, 161 methylation, 6, 160 Safranines applications, 3, 196 Safrole derivatives toxicity, 1, 139-140 occurrence, 6, 781 Safrole, 1-hydroxy-toxicity, 1, 140 Salazosulfapyridine intestinal disorders and, 2, 517 Salicylaldehydes chroman synthesis from, 3, 782 Salicylanilides ... 

SAM-dependent methylation of salicylic acid. The salicyl alcohol derivative salicin, found in many species of willow (Salix species Salicaceae), is not derived from salicylic acid, but probably via glucosylation of salicylaldehyde and then reduction of the carbonyl (Figure 4.27). Salicin is responsible for the analgesic and antipyretic effects of willow barks, widely used for centuries, and the template for synthesis of acetylsalicylic acid (aspirin) (Figure 4.27) as a more effective analogue. 

Cathodic reduction of the trichloroacetates 673 affords 3-chloro-coumarins in moderate yield (Equation 272). When salicylaldehyde derivatives 674 are reduced a mixture of 3-chloro-coumarins and ( )-l-chloro-2-(2-chloroprop-l-enyl)benzenes 675 are formed (Equation 273) <2003T9161, 1999JEC201>. 

Salicylaldehydes and some o-hydroxyaryl ketones react with Meldrum s acid to give coumarin-3-carboxylic acids <03TL1755>. 3-Cyanocoumarins, and thus the 3-carboxylic acids, are available in high yield from a Knoevenagel reaction between salicylaldehydes and malononitrile in water <0382331>. 3-Chlorocoumarins result from the cathodic reduction of trichloroacetyl esters of o-hydroxyacetophenones <03T9161>. 

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