Aryl, heteroaryl, and alkenyl cyanides are prepared by the reaction of halides[656-658] or triflates[659,660] with KCN or LiCN in DMF, HMPA, and THF. Addition of crown ethers[661] and alumina[662] promotes efficient aryl and alkenyl cyanation. lodobenzene is converted into benzonitrile (794) by the reaction of trimethylsiiyl cyanide in EtiN as a solvent. No reaction takes place with aryl bromides and chlorides[663]. The reaction was employed in an estradiol synthesis. The 3-hydroxy group in 796 was derived from the iodide 795 by converting it into a cyano group[664].  [c.246]

The nucleophilic reactivity of the oxygen has been observed in acetylation by acetic anhydride of 2-aryl- and 2-heteroaryl-A-2-thiazoline-4-ones (181) (388, 397, 410, 414, 416, 419, 422, 426. 427) and methylation of 5-(4 -chlorophenyl)-A-2-thiazoline-4-one (416) (Scheme 94).  [c.423]

The reaction of a thioamide with a-halocarbonyl compounds has been applied extensively, and many thiazoles (10) with alkyl, aryl, aralkyl, or heteroaryl functional groups at the three 2-, 4-, or 5-positions have been reported (Scheme 6).  [c.180]

Thiazolium salts with alkyl (103, 722), arylalkyl (116), aryl (305), or heteroaryl (96) substituents on the nitrogen have been also prepared by this procedure. As in the thiazole series, N-substituted thioamides can be formed directly in the reaction mixture from phosphorus pentasulfide and N-substituted amides (127). These methods are important in the synthesis of thiamine 102 (vitamin Bj) (Scheme 45).  [c.212]

By this general method, compound 172, in which R, = alkyl (231, 521, 561, 597), allyl (488), acetonyl (156), phenacyl (199, 292, 519), benzyl (272, 561). aryl (561), or carboxyalkyl (561), Rj = methyl (156. 199, 231, 561, 597). aryl (231, 270, 291, 561), or heteroaryl (231, 272, 292), and Rs = hydrogen, acetic acid (231), sulfur (561), or ester (199), have been prepared (Table 11-26).  [c.266]

Water ammonia and methane share the common feature of an approximately tetra hedral arrangement of four electron pairs Because we describe the shape of a molecule according to the positions of its atoms rather than the disposition of its electron pairs however water is said to be bent and ammonia is trigonal pyramidal  [c.29]

One approach called enzymatic resolution, involves treating a racemic mixture with an enzyme that catalyzes the reaction of only one of the enantiomers Some of the most commonly used ones are lipases and esterases enzymes that catalyze the hydrol ysis of esters In a typical procedure one enantiomer of the acetate ester of a racemic alcohol undergoes hydrolysis and the other is left unchanged when hydrolyzed m the presence of an esterase from hog liver  [c.312]

A mechanism consistent with these facts is presented m Figure 19 7 The six steps are best viewed as a combination of two distinct stages Formation of a tetrahedral intermediate characterizes the first stage (steps 1-3) and dissociation of this tetra hedral intermediate characterizes the second (steps 4-6)  [c.811]

Steps 2 and 4 are proton transfer reactions and are very fast Nucleophilic addi tion to the carbonyl group has a higher activation energy than dissociation of the tetra hedral intermediate step 1 is rate determining  [c.855]

There are good reasons to consider extending the class of cyanine-type chromogens to the older and well-known group of basic dyes (15). In a diphenylmethane dye such as Michler s Hydrol Blue (10), one ring contributes two double bonds in order to give an odd-alternate system. Aromatic-ring systems can be made part of the conjugated chain of a cyanine without altering the characteristic properties of the chromogen (13,16).  [c.297]

Disconnect the column, and remove the flask from the oil-bath. Add 25 ml. of dilute hydrochloric acid to the flask, shake the contents vigorously, and chill in ice-water, when crystals of benzhydrol will separate. (Occasionally the hydrol will separate initially as an oil, which ciystallises on vigorous stirring.)  [c.154]

Disconnect the column, and remove the flask from the oil-bath. Add 25 ml. of dilute hydrochloric acid to the flask, shake the contents vigorously, and chill in ice-water, when crystals of benzhydrol will separate. (Occasionally the hydrol will separate initially as an oil, which crj stallises on vigorous stirring.)  [c.154]

Arylvinylthiazoles (12) were prepared from 11 and bromomethyl-ketones (Scheme 7) (576), with Rj = aryl or heteroaryl groups (576) and R2 = Ph (80 to 95% yield) and Me (50 to 60% yield).  [c.184]

Thiazoles with Heterocyouc Substituents. Thiazoles with heterocyclic substituents in the 2- or 4-position have been synthesized (Table II-9). Thus thioacetamide (or its a-substituted derivatives) react with bromomethyl heteroarylketones under reflux in alcohol to give the corresponding 2-methyl-4-heteroarylthiazoles heteroaryl groups in the 4-position were 2 -thienyl (213, 692) a-pyrrolyl and 3-method derivatives  [c.195]

Ethyl-4-thiazoie carboxylate and derivatives (65) prepared by treating a suitably substituted ethylbromopyruvate (48) with a thioainide (2), followed by hydrolysis ga e the corresponding 4-carboxythiazoles (66) (Scheme 30), which can be also prepared ip good yields from a-bromopyruvic acid (250, 787). These compounds are convertible into 4-hydrazides, azides, and other functional derivatives in the usual manner, By a suitable choice of starting material, the 2-substituent (Rj) may be hydrogen, alkyl, or aminomethyl and derivatives (19, 220, 221, 247, 273, 281, 295, 486, 489, 795), phenyl (208, 299, 603), aryl (786), heteroaryl (557), or esters (298) and the 5-substituent (Rj) may be hydrogen (208, 220, 221, 247, 281, 298, 486, 603), aryl (299, 489), ester (103, 110, 145, 298, 577, 639), benzoyl (728), Or acetyl (786).  [c.204]

Ethyl-4,5-thiazole dicarboxylates (77), R =H, Me, Et, Ph, or heteroaryl, were prepared from diethyl-a-chloro-/3-ketosuccinate (76) and thioamides in boiling ethanol (Scheme 35) (103, 110, 145, 298, 577, 639).  [c.206]

Thiazolium salts can be obtained successfully by a modification of the Hantzsch s thiazole synthesis. This method is particularly valuable for those thiazolium compounds in which the substituent on the ring nitrogen cannot be introduced by direct alkylation, for example, aryl or heteroaryl thiazolium salts (Scheme 42).  [c.211]

In the same way, some polysubstituted derivatives (78, 91, 254, 303, 435, 478), 4-a- or /3-naphthyl (436, 496), 4-heteroaryl-2-aminothiazoles (153, 272, 422, 538, 569, 677, 680, 692, 735, 736, 752, 793), 2-aminothiazole sulfonyl derivatives (671. 798), 2-amino-4-(4-alkyl-selenophenyOthiazoles (631), and 4-substituted 2-aminothiazoles (691) have been also reported (Table 11-13).  [c.216]


This reaction has been widely studied, and a great variety of compounds (124), with Ri = methyl (8, 36, 62, 68, 78, 178, 616, 621), benzyl (600), phthalimidomethyl (650), alkyl (555, 583, 796), acetyl (78, 582, 655), phenyl (8, 23, 36, 39, 255, 338, 398, 423, 508, 510, 583, 586, 601, 650, 800), aryl (737, 793), a- and -naphthyl (399, 400, 423,. 599, 604, 617, 621, 653), -pyridyl (680), -quinolyl (680), heteroaryl (810), or NHCONHMe (799), were prepared in fairly good yields by either Method A or B (Table II-15  [c.233]

FIGURE 20 3 An acid cat alyzes the hydrolysis of a carboxylic acid anhydride by increasing the rate of the first stage of the mecha nism The faster the tetra hedral intermediate is formed the faster the rate of hydrolysis  [c.844]

Hysterosalpingography Hystrene Hysulf process Hytemp HyTex Hytrel  [c.504]

Separation, combustion, pyrolysis, hydrogena-tion, anaerobic fermen-tation, aerobic fermen-tation, biophotolysis, partial oxidation, steam reforming, chemical hy-drolysis, enzyme hydrol-ysis, other chemical conversions, natural processes  [c.15]

See pages that mention the term Hytrel : [c.262]    [c.262]    [c.412]    [c.437]    [c.111]    [c.112]    [c.178]    [c.180]    [c.182]    [c.193]    [c.194]    [c.195]    [c.196]    [c.197]    [c.198]    [c.420]    [c.453]    [c.333]    [c.2]    [c.870]    [c.493]    [c.493]    [c.632]    [c.632]    [c.632]   
Plastics materials (1999) -- [ c.55 , c.695 , c.737 , c.790 , c.879 ]