Molecular rearrangements 1,2-migration

For books, see Mayo, P. de Rearrangements in Ground and Excited States, 3 vols. Academic Press NY, 1980 Stevens, T.S. Watts, W.E. Selected Molecular Rearrangements Van Nostrand-Reinhold Princeton, 1973. For a review of many of these rearrangements, see Collins, C.J. Eastham, J.F. in Patai The Chemistry of the Carbonyl Group, vol. 1 Wiley NY, 1966, p. 761. See also the series Mechanisms of Molecular Migrations. 

It is well known that trialkylsilyl groups are prone to migrate via different types of molecular rearrangements [131]. This behavior serves to explain some... 

The initial intermediate 33 is the normal bis-(N — Si)-coordinated complex, which is obtained in analogy to numerous other neutral hexacoordinate complexes 30-38 (Eq. 15), prepared from SiC and various trichlorosilanes and substituted O-trimethylsilylated hydrazides. The final product 70 is the result of a novel molecular rearrangement, by which a chloride has been displaced by the dimethylamino-nitrogen and has migrated from carbon to silicon, accompanied by ring expansion and conversion of the N -> Si to O -> Si coordination. 

In several ways this reaction resembles the molecular rearrangements involving transitory carbonium ions. The reaction is acid-catalyzed60 (see the Schmidt reaction). In the presence of triphenylmethyl free radicals no mixed products are formed.61 The migrating group never leaves the field of the electronically deficient atoms concerned since the Curtius reaction with (—)o-(2-methyl-6-nitrophenyl)-benzoic acid (LXXV) produces an optically active amine62 (LXXVI). 

CXVIII, which will form lactams and are therefore cis to each other.756 As in the other molecular rearrangements, the migrating group never leaves the vicinity of the atoms which are concerned. Thus when a Hofmann reaction is carried out with (+) 3,5-dinitro-2-[a-naphthyl]-benzamide (CXIX) (which owes its optical activity to the restricted rotation of the bond connecting the benzene and naphthalene nuclei) an optically active amine (CXX) is formed 76 which has the same configuration as the starting material.77... 

The definition of molecular rearrangement includes changes in which there is a migration of an atom or... 

This means the synthesis must employ a reaction that generates an amine of 1 less carbon from succinic anhydride. Such a reaction is the Hofmann degradation of amides. As seen below, the reaction involves the migration of a group from carbonyl carbon to the adjacent nitrogen atom. It is therefore an example of a molecular rearrangement. ... 

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