Aminonitriles ring closures with

Primary and secondary y- and 8-aminonitriles may lead to ring closure to form five-and six-membered compounds, respectively. For example, the hydrogenation of 2-nitro- or 2-amino-4,5-dimethoxyphenylacetonitrile with Raney Ni gives 5,6-dimethoxyindole (eq. 7.58).109... 

The reaction of 2-aminobenzonitriles 12 (X = CH = CH Y = CH) with carbon disulfide in pyridine solution constitutes a convenient, one-step synthesis of quinazoline-2,4(l//,37/)-dithiones 14. The reaction is also generally applicable to heterocyelic 2-aminonitriles 12 (X = NH Y = N) which afford fused pyrimidinedithiones 14. The reaction proceeds via the intermediate formation of 13 which rearranges rapidly and irreversibly by a base-catalyzed ring-opening-ring-closure sequence to give the observed product. ... 

Anodic oxidation of enamines in NaCN-MeOH with iodide ion as mediator provides ring-fused cyclopropane aminonitriles with the nitrile group exclusively in exo position [Eq. (29)] [256]. This reaction is possibly an electrocyclic ring closure of an intermediate allyl cation LXXIII. 

In a conventional seven-step synthesis beginning with biphenylene, biphenylene-2-acetonitrile (100), mp. 105—107°, was prepared. It condenses readily with (7) to the orange-yellow aminonitriles (101) (not isolated). In accordance with the MO calculation the ring-closure to the benz(b)biphenylene-6-carbonitriles (102) is strongly favored, theoretically by 0.211 / (Section II. C., Fig. 1 VIII), over the isomeric benzo(a)biphenylenes of which no traces could be detected in the reaction products59. By hydrolysis and decarboxylation (102 a) was converted to benzo(b)-biphenylene, mp. 236-237°, Ref. 242-243°60). 

The reaction of amidines with o-aminonitriles to give (fused) 4-amino-pyrimidines was introduced by Taylor and Ehrhart in I960.90 The reaction is thought to proceed through the more complex amidine of type 114, in which R (the methyl group of acetamidine for instance) becomes an alkyl group in the 2-position of the product. At the temperatures used, ring closure is rapid, and no intermediate such as 114 has been isolated. 

A soln. of CIO2 added slowly to a soln. of 3-piperidinopropan- l-ol in Na-borate buffer with simultaneous addition of aq. NaOH to maintain a pH of 9.0 - 5-oxa-l-azabi-cyclo[4.4.0]decane. Y 67%. With unsym. substrates, ring closure takes place at the least subst. a-position (in contrast with Hg(II)-oxidation). F.e., also a-aminonitriles from amines, s. C.-K. Chen et al., J. Am. Chem. Soc. 110, 4829-31 (1988). 

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