Cyanides rearrangement

Potential surfaces for the isocyanide-cyanide rearrangement have been constructed from extended Hiickel calculations and theory predicts a small amount of charge separation in the transition state . The data on methyl and ethyl iso-... 

Preparation of cyanides.1 An attractive route to cyanides involves as the first step dehydration of alkylformamides with phosgene-tricthylamine (1,857) or phosphoryl chloride-diisopropylamine (13,249) to form isocyanidcs followed by isocyanidc-cyanide rearrangement. This rearrangement traditionally was conducted in the gas phase, but proceeds in almost quantitative yield when carried out by flash pyrolysis at 600°. This route to cyanides is attractive because allyl isocyanides rearrange without allylic rearrangement. Moreover, optically active carboxylic acids can be obtained from optically active amines without raccmization. 

A high-yield access to cyanides from isocyanides is given by the isocyanide-cyanide rearrangement [1215, 1216], Isocyanides are converted to cyanides by flash thermolysis in excellent yields (often near 100%) under strict retention of conflgu-ration. The employed isocyanides were prepared by standard procedures from the corresponding formamides by the use of phosphoryl chloride. A 1-homocubyl isocyanide was synthesized in 51% yield [1216],... 

Characteristic fragmentations of quinone structures and cleavages involving cyanide rearrangement are responsible for most of the total ion current (see Scheme 1.7). 

Finally a general approach to synthesize A -pyrrolines must be mentioned. This is tl acid-catalyzed (NH4CI or catalytic amounts of HBr) and thermally (150°C) induced tea rangement of cyclopropyl imines. These educts may be obtained from commercial cyan> acetate, cyclopropyl cyanide, or benzyl cyanide derivatives by the routes outlined below. Tl rearrangement is reminiscent of the rearrangement of 1-silyloxy-l-vinylcyclopropancs (p. 7 83) but since it is acid-catalyzed it occurs at much lower temperatures. A -Pyrrolines constitut reactive enamines and may be used in further addition reactions such as the Robinson anei lation with methyl vinyl ketone (R.V. Stevens, 1967, 1968, 1971). 

Synthesis of the remaining half of the molecule starts with the formation of the monomethyl ether (9) from orcinol (8). The carbon atom that is to serve as the bridge is introduced as an aldehyde by formylation with zinc cyanide and hydrochloric acid (10). The phenol is then protected as the acetate. Successive oxidation and treatment with thionyl chloride affords the protected acid chloride (11). Acylation of the free phenol group in 7 by means of 11 affords the ester, 12. The ester is then rearranged by an ortho-Fries reaction (catalyzed by either titanium... 

The vapor-phase chlorination reaction occurs at approximately 200-300°C. The dichlorobutene mixture is then treated with NaCN or HCN in presence of copper cyanide. The product 1,4-dicyano-2-butene is obtained in high yield because allylic rearrangement to the more thermodynamically stable isomer occurs during the cyanation reaction ... 

Trimethylacetic acid may be made by the hydrolysis of tert-butyl cyanide with weak hydrochloric acid at ioo0.1 It is also obtained by oxidation of trimethylpyroracemic acid with silver oxide or potassium dichromate and sulfuric acid,2 by oxidation of tertf-butylethylene with permanganate solution,3 or by oxidation of dimethyl 2,2-propanol with chromic acid.4 Schroeter reports the formation of trimethylacetic acid by rearrangement of the oxime of trimethylacetophenone to give the anilide of trimethylacetic acid, which can be hydrolyzed to give the acid.5... 

The sequence depicted has been suggested as a plausible reaction mechanism. Diazabasketene primarily reacts via a retro-Diels-Alder reaction to give an azine which, after a Cope rearrangement, undergoes a further retro-Diels -Alder reaction to cleave off hydrogen cyanide. The resulting azabicyclo[4.2.0]octatriene finally isomerizes to the target molecule. 

The arenediazocyanides have been known since 1879. They played an important role in the Hantzsch-Bamberger debate on the (Z)/( ,)-isomerism of diazo compounds (see Sec. 7.1). When an aqueous solution of a diazonium salt is added to a solution of sodium or potassium cyanide, both in relatively high concentration, at a temperature below 0°C, a yellow to red (Z)-arenediazocyanide starts to crystallize. Hantzsch and Schulze (1895 a) found that these compounds rearrange into the (ii)-isomers, which have a bathochromically shifted visible absorption (see Sec. 7.1). Under strongly alkaline conditions a 1 2 adduct is formed, to which Stephenson and Waters (1939) assigned the structure 6.36. It was never corroborated, however, by modern instrumental analysis. 

When aromatic nitro compounds are treated with cyanide ion, the nitro group is displaced and a carboxyl group enters with cine substitution (p. 854), always ortho to the displaced group, never meta or para. The scope of this reaction, called the von Richter rearrangement, is variable. As with other nucleophilic aromatic substitutions, the reaction gives best results when electron-withdrawing groups are in ortho and para positions, but yields are low, usually < 20% and never > 50%. 

It may be noted that 16 are stable compounds hence it should be possible to prepare them independently and to subject them to the conditions of the von Richter rearrangement. This was done and the correct products are obtained. Further evidence is that when 15 (Z=C1 or Br) was treated with cyanide in H O, one-half the oxygen in the product was labeled, showing that one of the oxygens of the carboxyl group came from the nitro group and one from the solvent, as required by this mechanism. ... 

If the rearrangement of oxime sulfonates is induced by organoaluminum reagents,the intermediate (71) is captured by the nucleophile originally attached to the Al. By this means an oxime can be converted to an imine, an imino thioether (R—N—C—SR), or an imino nitrile (R—N—C—In the last case, the nucleophile comes from added trimethyl si lyl cyanide. The imine-producing reaction can also be accomplished with a Grignard reagent in benzene or toluene. ... 

Coumalic acid, 56, 51 Crotyl fluoride, 57,73 18-CROWN-6,57, 30 Curtius rearrangement, 59, 1 Cyanide ion, as catalyst for conjugate addition of aldehydes, 59, 56 p-Cyanobenzenesulfonyl cyanide, 57, 89 2-( 1 -Cyanocyclohexyljhydrazinecarboxylic acid methyl ester, 58,102 Cy a noferrocene, 56, 30 Cyanogen chloride, 57, 88... 

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