Cyanoformates

These acids (51) are organic molecules that contain a plurality of cyano groups and are readily ionized to hydrogen ions and resonance-stabilized anions. Typical cyanocarbon acids are cyanoform, methanetricarbonitrile (5) 1,1,3,3-tetracyanopropene [32019-26-4] l-propene-l,l,3,3-tetracarbonitrile (52) 1,1,2,3,3-pentacyanopropene [45078-17-9], l-propene-l,l,2,3,3-pentacarbonitrile (51) l,l,2,6,7,7-hexacyano-l,3,5-heptatriene [69239-39-0] (53) 2-dicyanomethylene-l,l,3,3-tetracyanopropane [32019-27-5] (51) and l,3-cyclopentadiene-l,2,3,4,5-pentacarbonitrile [69239-40-3] (54,55). Many of these acids rival mineral acids in strength (56) and are usually isolable only as salts with metal or ammonium ions. The remarkable strength of these acids results from resonance stabilization in the anions that is not possible in the protonated forms. 

Photolysis of 2,3-diphenyl-A -azirine (442) generates benzonitrile ylide (443). Irradiation in the presence of ethyl cyanoformate resulted in a mixture of the oxazoline (444) and the imidazole (445) by 1,3-dlpolar cycloaddition to the carbonyl and nitrile group, respectively (72HCA919). 

The photochemical addition of azirines to the carbonyl group of aldehydes, ketones, and esters is also completely regiospecific (77H(6)143). Besides the formation of the isomeric oxazolines (50) from (39) and ethyl cyanoformate, there is also formed the imidazole (51) from addition to C=N in the expected regioselective manner. Thioesters lead to thiazolines (52), while isocyanates and ketenes produce heterocycles (53). 

Isonitriles and some nitriles can be viewed formally as having a nucleophihc center and an electrophilic center at the same skeleton atom Tnmethylsilylcyanide and cyanoformates add to hetero-1,3 dienes in a stepwise process to give five-mem bered rmg systems with the same stmcture as the isonitnle adducts [41],... 

The question of whether the commercially available benzoyl cyanide (PhCOCN), methyl cyanoformate (MeOCOCN), and R2NCOCN are formed (cf, however. Ref... 

Ketones are converted to (3-ketoesters by acylation with diethyl carbonate or diethyl oxalate, as illustrated by Entries 4 and 5 in Scheme 2.16. Alkyl cyanoformate can be used as the acylating reagent under conditions where a ketone enolate has been formed under kinetic control.227... 

Recently, Ohwada has employed benzoxazines as the starting precursor for various p,p-unsubstimted o-QMs (Fig. 4.4).3 In this protocol, the benzoxazine is gently warmed in some cases, 50 °C proves sufficient to expel methyl cyanoformate and... 

The (triphos)Ni0 template reacts with ethyl cyanoformate to give (220).648 The MO description and reactivity of the CS2 complex (221) has been studied in some detail.649 Treatment with 02 gives the dithiocarbonate compound (221a),650 while bubbling of C02 through a solution of (221) yields the carbonato complex (221b).651 In both cases, one of the phosphine arms has been oxidized and is found dangling. 

HCN is the most preferred cyanide source in cyanohydrin synthesis. Besides HCN, several different cyanide sources, like potassium cyanide, are being used in biotransformation. Alternative methods for the safe handling of cyanides on a laboratory scale are, for instance, to use cyanide salts in solution. These solutions can be acidified and used as the aqueous layer in two-phase systems or the HCN can be extracted into the organic layer with the desired solvent for reactions in an organic phase. After the reaction, excess cyanide can readily be destroyed with iron(II) sulfate, or iron(III) chloride or bleach. Cyanide can also be presented in the form of organic cyano, such as acetone cyanohydrin [46] or cyanoformates. However, as claimed by Effenberger, some results could not be reproduced [47]. 

Cyclon Methyl Cyanoformate and Ethyl Cyanoformate Mixture CIO-A... 

Similar to reactions of iodopyrimidines previously mentioned in Section 6.2.2.2 (60 —> 61), the Grignard reagent 171, efficiently prepared from halopyridazine 170, was quenched with electrophiles such as acetaldehyde, ethyl cyanoformate, DMF or phenylsulfide to give 172 in acceptable yields <00T265>. 

The reaction of IV-alkyl- and iV-arylhydroxylamines with ethyl cyanoformate (193) leads to carbethoxyamino nitrones (194) (Scheme 2.68), which appear to be excellent starting materials for the synthesis of various nitrogen-bearing... 

Butyl cyanoformate, 44, 19 see-Butyl 0,0-dimethylacrylate, 41, 62 Butylhydrazinium hydrogen sulfate, 43, 2... 

Butyl hydrazodiformate has been prepared by acylation of /-butyl carbazate by means of /-butyl azidoformate 3 4 or /-butyl cyanoformate.5 /-Butyl azodiformate has been prepared only by oxidation of the hydrazo compound. ... 

The reactions of ethyl cyanoformate and dialkyl malonates in the presence of zinc chloride and triethylamine, or in the presence of TiCl4 or SnCl4 in methylene chloride at reflux temperature for 3 hr, or at room temperature overnight, gave amino(alkoxycarbonyl)methylenemalonates (314, R1 = Et) in good yields [79TL2525 81JAP(K)71050],... 

Amino(alkoxycarbonyl)methylenemalonates (314) were also prepared in good yields in the reactions of dialkyl cyanoformate and bromo- or chloromalonates in the presence of SnCl2 or TiCl3 in benzene, or in the presence of zinc activated by copper in THF, [81JAP(K)71049, 81JAP(K)87542]. 

Calcium azide, 3936 f Carbon disulfide, 0560 Chlorine dioxide, 4042 Chloroacetylene, 0652 Chloryl perchlorate, 4104 Copper(I) azide, 4287 Cyanamide, 0404 Cyanoform, 1383 Cyanogen bromide, 0313 Cyanogen chloride, 0323 Cyanogen fluoride, 0323... 

The transient C-nitrosoimine 193 (Ar = 4-CIC6H4) is formed by the action of ethyl cyanoformate on the sulfimide 191 and also by the oxidation of the amidoxime 192 with lead tetraacetate. In the presence of thebaine, both reactions yield an identical dihydrooxazine101. 

CuCN-2LiCl. This can then be selectively allylated vith allyl bromide to provide the dibromoimidazole 36, which can now be magnesiated by treatment with a further equivalent of iPrMgBr, providing the ester-substituted imidazole 37 in 55% yield after carboxylation with ethyl cyanoformate [25]. 

Lundgren, S. Wingstrand, E. Penhoat, M. Moberg, C. Dual Lewis acid-Lewis base activation in enantioselective cyanation of aldehydes using acetyl cyanide and cyanoformate as cyanide sources. J. Am. Chem. Soc. 2005,127, 11592-11593. 

D-Triazoles have been isolated from the reaction of several activated nitriles, such as cyanogen, cyanogen halides, methyl cyanoformate, and cyanic acid esters, with diazoalkanes. The reaction can formally be regarded as a 1,3-dipolar cycloaddition. The v-triazoles may be... 

Cyanation of aldehydes and ketones is an important chemical process for C C bond formation." " Trimethylsilyl cyanide and/or HCN are commonly used as cyanide sources. The intrinsic toxicity and instability of these reagents are problematic in their applications. Acetyl cyanide and cyanoformates were used as cyanide sources in the enantioselective cyanation of aldehydes catalyzed by a chiral Ti complex and Lewis base (Scheme 5.31)." The Lewis base was necessary for the good yields and selectivities of these reactions. The desired products were obtained in the presence of 10mol% triethyl amine and 5mol% chiral titanium catalyst (Figure 5.14). Various aliphatic and aromatic aldehydes could be used in these reactions. 

When ethyl cyanoformate was used as the cyanide source and a heterobimetallic YLi3(binaphthoxide) complex (YLB) (Figure 5.15) was used as catalyst, asymmetric cyanoethoxycarbonylations of aldehydes were achieved in high yields and enantioselectivities in the presence of three achiral additives water, tris(2,6-... 

In addition to metal catalysts, organocatalysts could also be used in asymmetric cyanation reactions. Chiral Lewis bases, modified cinchona alkaloids, catalyzed asymmetric cyanation of ketones by using ethyl cyanoformate as the cyanide source (Scheme 5.34)." Similar to metal-catalyzed reactions, ethyl cyanoformate was first activated by chiral Lewis bases to form active nucleophiles. Various acyclic and cyclic dialkyl ketones were transformed into the desired products. Because of using... 

Synthesis of p-Ketoesters by C-Acylation of Preformed Enolates with Methyl Cyanoformate Preparation of (la,4ag,8ao)Methyl 2-Oxo-decahydro-l-naphthoate... 

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