Methyl nitrile, substitution

A few years after the first publication on acylamino acid thiophenyl esters [4] the peptide research team of the CIBA laboratories in Basel, led by Robert Schwyzer, described a systematic study of the aminolysis of methyl esters substituted with various electron-withdrawing groups [20]. From a series of esters examined with respect to their reaction rates in aminolysis cyanomethyl esters were selected as best suited for peptide synthesis. Cyanomethyl esters were readily prepared through the reaction of acylamino acid salts with chloroaceto-nitrile and they showed satisfactory rates in the acylation of amino acid esters... 

As improvements over P-methylumbeUiferone (55—57), 4-methyl-7-amino-coumarin [26093-31-2] (12a) and 7-dimethylamino-4-methylcoumarin [87-014] (12b) (58—61) were proposed. These compounds are used for brightening wool and nylon either in soap powders or detergents, or as salts under acid dyeing conditions. They are obtained by the Pechmaim synthesis from appropriately substituted phenols and P-ketocarboxyflc acid esters or nitriles in the presence of Lewis acid catalysts (see Coumarin). 

Nitrile ylides derived from the photolysis of 1-azirines have also been found to undergo a novel intramolecular 1,1-cycloaddition reaction (75JA3862). Irradiation of (65) gave a 1 1 mixture of azabicyclohexenes (67) and (68). On further irradiation (67) was quantitatively isomerized to (68). Photolysis of (65) in the presence of excess dimethyl acetylenedicar-boxylate resulted in the 1,3-dipolar trapping of the normal nitrile ylide. Under these conditions, the formation of azabicyclohexenes (67) and (68) was entirely suppressed. The photoreaction of the closely related methyl-substituted azirine (65b) gave azabicyclohexene (68b) as the primary photoproduct. The formation of the thermodynamically less favored endo isomer, i.e. (68b), corresponds to a complete inversion of stereochemistry about the TT-system in the cycloaddition process. 

A thioamide of isonicotinic acid has also shown tuberculostatic activity in the clinic. The additional substitution on the pyridine ring precludes its preparation from simple starting materials. Reaction of ethyl methyl ketone with ethyl oxalate leads to the ester-diketone, 12 (shown as its enol). Condensation of this with cyanoacetamide gives the substituted pyridone, 13, which contains both the ethyl and carboxyl groups in the desired position. The nitrile group is then excised by means of decarboxylative hydrolysis. Treatment of the pyridone (14) with phosphorus oxychloride converts that compound (after exposure to ethanol to take the acid chloride to the ester) to the chloro-pyridine, 15. The halogen is then removed by catalytic reduction (16). The ester at the 4 position is converted to the desired functionality by successive conversion to the amide (17), dehydration to the nitrile (18), and finally addition of hydrogen sulfide. There is thus obtained ethionamide (19)... 

Condensation of 165 with ethoxymethylenemalononitrile gave 171, and with ethyl ethoxymethylenecyanoacetate or methyl bis(methylmercapto)-methylene cyanoacetate it yielded 172 (80AP108). The reaction of 172 with urea, thiourea, and benzyl nitrile afforded 173 (91PHA98). Treatment of hydrazino derivatives 165 with alkyl, aryl, or aralkyl isothiocyanates yielded (86JHC1731) 3-(/V-substituted-thiocarbamoyl)-hydrazino[l,2,4]triazino[5,6-b]indoles which have been evaluated for in vitro antimicrobial activity (Scheme 36). 

Transformation of the amino nitriles to the corresponding amino acids, with removal of the dioxane ring, is carried out in two steps. Treatment with concentrated hydrochloric acid results in the hydrolysis of both the nitrile and the acetal group, and in cyclization to the corresponding 3-substituted 5-hydroxyniethyl-3-methyl-2-oxo-6-phenylmorpholinc hydrochlorides. Oxidative cleavage with 2 N sodium hydroxide solution, air and Raney nickel at 120 CC (ca. 30 h) delivers the hydrochlorides of the free a-methylamino acids in high yield. 

Nitriles are organic derivatives of hydrocyanic acid in which the substituting group is attached to carbon. Their formula is R.C N. Because most nitriles can be derived from corresponding acid amides, R.CO.NH2, by removal of w, they are called nitriles. For instance, the compd CH3.CN is called acetonitrile because it is derived from acetamide. It can also be called methyl cyanide. The compd C2HS.CN is called either propionitrile or ethyl cyanide, etc The first nitrile to be prepared was propionitrile which J. Pelouze obtained in 1834 by distg Ba ethyl sulfate with K cyanide... 

Ethyl 3-azido-l-methyl-177-indole-2-carboxylate 361 is prepared in 70% yield by diazotization of amine 360 followed by substitution of the created diazonium group with sodium azide. In cycloadditions with nitrile anions, azide 361 forms triazole intermediates 362. However, under the reaction conditions, cyclocondensation of the amino and ethoxycarbonyl groups in 362 results in formation of an additional ring. This domino process provides efficiently 4/7-indolo[2,3-i ]l,2,3-triazolo[l,5- ]pyrimidines 363 in 70-80% yield (Scheme 57) <2006TL2187>. 

It is of course possible to name individual radialenes according to IUPAC rules [e.g. per(methylene)cycloalkanes 1-4]. However, the descriptiveness of the term radialene may some day pave its way into the official nomenclature. For substituted [ ]radialenes we have proposed1 a pragmatic numbering system, in which an inner ring is numbered first, followed by an outer ring . The numbering of substituents should follow IUPAC rules. Thus, the hydrocarbon 7 is 4,4-diethyl-5,5-dimethyl[3]radialene, the ester 8 should be called 7-methoxycarbonyl-5,5-dimethyl[4]radialene, the nitrile 9 which can exist in four diastereomeric forms is (6Z,7Z)-6-cyano-5,5,7-trimethyl[4]radialene and the difunctionalized [5]radialene 10 is (7 ,6Z)-7-bromo-6-formyl-6-methyl[5]radialene. 

This regioselectivity is practically not influenced by the nature of subsituent R. 3,5-Disubstituted isoxazolines are the sole or main products in [3 + 2] cycloaddition reactions of nitrile oxides with various monosubstituted ethylenes such as allylbenzene (99), methyl acrylate (105), acrylonitrile (105, 168), vinyl acetate (168) and diethyl vinylphosphonate (169). This is also the case for phenyl vinyl selenide (170), though subsequent oxidation—elimination leads to 3-substituted isoxazoles in a one-pot, two-step transformation. 1,1-Disubstituted ethylenes such as 2-methylene-1 -phenyl-1,3-butanedione, 2-methylene-1,3-diphenyl- 1,3-propa-nedione, 2-methylene-3-oxo-3-phenylpropanoates (171), 2-methylene-1,3-dichlo-ropropane, 2-methylenepropane-l,3-diol (172) and l,l-bis(diethoxyphosphoryl) ethylene (173) give the corresponding 3-R-5,5-disubstituted 4,5-dihydrooxazoles. 

Cycloalkene Derivatives Cyclopropenes readily interact with nitrile oxides. Reactions of a broad series of 3,3-disubstituted cyclopropenes with 4-substituted benzonitrile, methoxycarbonyl- and cyanoformonitrile oxides (229) as well as with di(isopropoxy)phosphorylformonitrile oxide (230) give 2-oxa-3-azabicyclo[3.1.0]hexene derivatives 62. Stereoselectivity of the cycloaddition is governed by both steric and polar factors. In particular, steric factors are supposed to prevail for 3-methyl-3-phenylcyclopropene affording 62 [R1 =... 

Heterocycles Both non-aromatic unsaturated heterocycles and heteroaromatic compounds are able to play the role of ethene dipolarophiles in reactions with nitrile oxides. 1,3-Dipolar cycloadditions of various unsaturated oxygen heterocycles are well documented. Thus, 2-furonitrile oxide and its 5-substituted derivatives give isoxazoline adducts, for example, 90, with 2,3- and 2,5-dihydro-furan, 2,3-dihydropyran, l,3-dioxep-5-ene, its 2-methyl- and 2-phenyl-substituted derivatives, 5,6-bis(methoxycarbonyl)-7-oxabicyclo[2.2.1]hept-2-ene, and 1,4-epoxy-l,4-dihydronaphthalene. Regio- and endo-exo stereoselectivities have also been determined (259). 

Dipolar cycloaddition of 2,4-(trimethylsilyl)- and 2,4-(trimethylgermyl)-substituted thiophene-1,1-dioxides as well as silylated 2,2 -bithiophene-1,1-dioxides was investigated. It was shown that only the C(4)=C(5) double bond of 2,4-disubstituted thiophene-1,1-dioxides interacts with acetonitrile oxide to give thienoisoxazoline dioxides. Bithiophene derivatives were inactive or their reaction with nitrile oxide was accompanied by desilylation. Cycloaddition of benzonitrile oxide with all mentioned sulfones did not occur. The molecular structure of 3a-methyl-5.6a-bis(trimethylgermyl)-3a,6a-dihydrothieno 2.3-c/ isoxazole 4,4-dioxide was established by X-ray diffraction (263). ... 

Dipolar cycloaddition reaction of trimethylstannylacetylene with nitrile oxides yielded 3-substituted 5-(trimethylstannyl)isoxazoles 221. Similar reactions of (trimethylstannyl)phenylacetylene, l-(trimethylstannyl)-l-hexyne, and bis (trimethylsilyl)acetylene give the corresponding 3,5-disubstituted 4-(trimethyl-stannyl)isoxazoles 222, almost regioselectively (379). The 1,3-dipolar cycloaddition reaction of bis(tributylstannyl)acetylene with acetonitrile oxide, followed by treatment with aqueous ammonia in ethanol in a sealed tube, gives 3-methyl-4-(tributylstannyl)isoxazole 223. The palladium catalyzed cross coupling reaction of... 

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