Rearrangements involving cyanides

A number of rearrangements involving loss and gain of cyanide groups has also been observed (14), for example, the interconversion of the pentacyanocobalt complex (17) and tetracyanocobalt complex (18) (26). 

The main biological and biochemical interest in cobalt concerns vitamin B,2 and a number of its derivatives, such as 5 -deoxyadenosyl cobalamin, which function as coenzyme in a number of rearrangements involving hydrogen shifts and aquocobalamin which is involved in the synthesis of methionine, methane and acetate. Vitamin in its resting state is ESR-inactive since it contains Co , but, when reduced to Co, spectra such as that shown in Figure 4.7 are obtained. This reduced form is referred to as vitamin B,2r it does not have cyanide as a sixth ligand. Its... 

A summary of the applications of this rearrangement to indole synthesis by Makisumi and Takada is illustrated in Scheme 4. In the case of reactions involving cyanide (equation 3), when R=H, the 2-cyano-3-methylindoles are also isolated in 7%-9% yield resulting from nucleophilic attack at the C-2 indolenium ion formed by loss of hydroxide from 9. Likewise, the extensions of Thyagarajan s initial result to the synthesis of other indoles are shown in Scheme 5. 

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

The second method involves the reaction of benzophenone with sodium cyanide in the presence of ammonium carbonate, followed by the simultaneous cyclization of the resulting product (carboxyaminoninile) and its rearrangement under the reaction conditions to form phenytoin [2]. 

Two one-pot syntheses of highly substituted pyran-2-ones have been published. One involves the reaction between t-BuNC, dialkyl acetylenedicarboxylates and bromomalonates <99JCR368>. In the other, cyclobutenediones are treated with 0-silylated cyanohydrins to yield a 4-acylcyclobutenone by a 1,4-silyl migration and cyanide displacement which rearranges to the pyranone (Scheme 18) <99JOC2145>. 

It is thus clear that thermal rearrangements of 2,3-diazido-l,4-quinones proceed in two discrete stages. The first involves the formation of the diacyl cyanides and 2-azido-2-cyano-l,3-cyclopentenediones the second entails the subsequent ring expansion of these cyclic azides to 2-aza-3-... 

The heating of lactones with powdered alkali cyanides leads to salts of cyano acids. The procedure is illustrated (above equation) by the synthesis of o-carboxybenzyl cyanide from phthalide and potassium cyanide (67-83%). In another instance, the reaction of potassium Cyanide with y-anisyl-y-butyrolactone involves a rearrangement thereby forming a /3-cyano acid instead of the anticipated y-cyano acid, ... 

Ring expansion of the bicyclic isothiazole (698) occurred upon treatment with cyanide ion to give the imidazo[l,2-c][l,3]thiazine (699). The mechanism involves initial ring opening by attack on sulfur, and then ring closure. The anion of methyl propiolate also causes the same type of rearrangement (79TL1281). 

Potassium periodate has been used in place of iodate for various titrations involving the iodine-chloride, iodine-bromide, and iodine-cyanide end points. Reaction of periodate with iodide involves transfer of an oxygen atom rather than an electron, followed by rearrangement of the structure of the IO4" ion. In the oxidation of the active oxidant appears to be 104 . An intermediate... 

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