Beckmann reaction intramolecular

Nitrones derived from 2-azabicyclo[5.3.0]decane give quinolizidine compounds by photochemical Beckmann rearrangement which implies simultaneous ring expansion and ring contraction reactions. Intramolecular Schmidt reactions in 2(4-azidobutyl)-cyclopentanones also give quinolizidinone derivatives by ring expansion. Examples of both types of reactions are given in Sections 12.01.11.1 and 12.01.11.3, respectively. 

One of the most useful variants of the Beckmann reaction is that in which the intermediate is trapped with a nucleophile other than water. Both carbon and heteroatomic nucleophiles have been used in this context. Intramolecular interception gives cyclized products. 

Benzoxazoles have been prepared by intramolecular reaction of a phenolic —OH groiq) with a Beckmann intermediate (equation 30). A cyclic imidate was isolated in high yield from tosylation and in situ Beckmann reaction of the erythromycin-derived oxime (4[Pg.698]

When the nucleophile is already present as a part of the starting oxime (for example, a heteroatom or a C=C double bond), intramolecular trapping of the electrophilic intermediate is possible and a new cycle is formed. This transformation is usually referred to as a Beckmann Rearrangement-Cychzation reaction. Two modes of ring closure may be possible, depending on the oxime structure (equations 111 and 112) ... 

This surprising result was reported by B. Amit and A. Hassner, Synthesis, 1978, 932. The expected reaction was the Beckmann rearrangement (Chapter 37) but what actually happened was a Beckmann fragmentation (Chapter 38) followed by an intramolecular FriedetCrafts alkylation (Chapter 22). 

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