Hydroxy-alkyl-, hydration

Acetyl-2,4-dioxo-tetrahydropyrane bilden mit iiberschussigem Hydrazin-Hydrat zunachst isolierbare En-hydrazine, die zu 4-Hydrazinocarbonyl-3(5)-(2-hydroxy-alkyl)-5(3)-methyl-1 H-pyrazolen cyclisieren1193. 

Addition of hydrogen sulfide and thiols is qualitatively similar to reaction with alcohols in that there are two stages, formation of hemithioacetal (or hemithio-ketal) followed by acid-catalyzed elimination of the hydroxy group and substitution of a second —SR (Equations 8.47 and 8.48). The transformation has been studied less extensively than hydration and acetal formation, and relatively little information on mechanism is available. The initial addition appears to be specific base-catalyzed, an observation that implies that RS is the species that adds. The situation is thus similar to cyanide addition. General acid catalysis has, however, been found at pH 1 to 2 for addition of weakly acidic alkyl thiols, and the reaction rate as a function of pH has a minimum and rises both on the... 

A new efficient procedure has been proposed for the synthesis of 3-aryl-5-amino-l//-pyrazoles by reaction of a-chloro-/ -arylacrylonitriles with hydrazine hydrate <2004RJ01518>. Reaction of 2-(3,3-dicyano-2-propenylidene)-4,4,5,5-tetra-methyl-l,3-dioxolane 641 with hydrazine afforded 3-(2-hydroxy-l,l,2-trimethylpropoxy)pyrazole 642 (Equation 134) <2003RJ01016>. Treatment of ethyl 3,3-dicyano-2-methoxyacrylate with alkyl, aryl, heterocyclic, and sulfonyl hydrazines led to the synthesis of N-l-substituted 3-acyM-cyano-5-aminopyrazoles, which are versatile intermediates for the synthesis of many biologically active scaffolds <2006TL5797>. 2-Hydrazinothiazol-4(5//)-one reacted with a variety of cinnamonitrile derivatives and activated acrylonitriles to yield annelated pyrazolopyrano[2,3-rf thiazole <1998JCM730>. 

Treatment of lithium acetylide with a primary alkyl halide (bromide or iodide) or with aldehydes or ketones produces the corresponding monosubstituted acetylenes or propargylic alcohols. Mercuric ion-catalyzed hydration of these furnishes methyl ketones and methyl a-hydroxy ketones, respectively. 

Die Acyloxy-Gruppc [vgl, Bd. X/2, S. 622 (1967)] wird leicht durch einen zweiten Arylhydrazin-Rest aus-getauscht, wobei 1 -Aryl-4-arylazo-5-hydroxy-l H-pyrazole entstehen. Mit Hydrazin-Hydrat bildcn sich aus 2-Acetoxy-3-oxo-alkansaure-estern in zumeist maBiger Ausbeute 3(5)-Alkyl-4,5(3)-dihydr-oxy-1 II-pyrazole322. 2-Phenoxy-(bzw. 2-Phenylthio)-3-oxo-alkansaurc-ester reagieren analog311. 

The use of trichloroacetaldehyde is also to be particularly noted. Although reactions between this aldehyde and various dialkyl hydrogenphosphonates have been report- 269,274,294,295 it is the dimethyl ester of (l-hydroxy-2,2,2-trichloroethyl)phosphonic acid which has received particular attention, and which has been studied widely from the structural point of view in the light of its commercial importance as the powerful insecticide dipterex (also known as trichlorphon and chlorophos). Polyfluoroalkyl esters of the related alkyl(l-hydroxy-2,2,2-trichloroethyl)phosphinic acids have been prepared by the unusual combination of chloral hydrate and the bis(polyfluoroalkyl) alkylphosphonite ester ... 

A single-step benzoylation-oximation has been described on 4-hydroxy-coumarin by the use of PhCCl=NOH and EtjN in boiling methanol. When 7-methoxy-8-prenylcoumarin (osthol) or its epoxide was treated with various Lewis acids, several products were obtained. These resulted from migration or disappearance of the exocyclic double bond, abnormal Friedel-Crafts phenyl-ation, hydration, cyclization, or demethylation. A novel ring-opening of coumarins was effected by treatment with alkyl halides and NaH in THF. The c/5-o-alkoxycinnamic acid was obtained mainly or exclusively. 

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