Claisen aliphatic, thermal

The aliphatic Claisen Rearrangement is a [3,3]-sigmatropic rearrangement in which an allyl vinyl ether is converted thermally to an unsaturated carbonyl compound. 

F. E. Ziegler, The thermal aliphatic Claisen rearrangement, Chem. Rev. 1988,88, 1423. 

When o-phcnylenediamine reacts with aliphatic or aliphatic-aromatic ketones the initially formed benzimidazolines can be thermally decomposed, losing a hydrocarbon fragment to yield 2-substituted benzimidazoles [81, 131]. While this method does not appear to have major synthetic importance, the analogous reaction with a, 6-diketonc has some application [132]. Presumably it involves an acid-catalysed retro-Claisen condensation of the S-dicarbonyl compound. When acetylacetonc is used, acetone is formed. The process, then, offers an unambiguous approach to compounds such as 2-methyl-4-nitrobenzimidazoles (not available by direct nitration). Neither the numbers of substituents on the arylenediamine nor their natures appear to affect yields or reaction times significantly. 

Example 1, Tandem Bamford-Stevens/thermal aliphatic Claisen rearrangement... 

The development of a tandem rhodium-catalyzed Bamford-Stevens/thermal aliphatic Claisen rearrangement sequence was elegantly demonstrated by Stoltz. As a general method to prepare non-carbonyl-stabilized diazo compounds in situ, this group chose to investigate the decomposition of //-aziridinyl imines (also known as Eschenmoser hydrazones) 28. ... 

The thermal rearrangement of allyl phenyl ethers to o-allyl phenol and its mechanism is very well known to organic chemists. Both the aliphatic and aromatic Claisen rearrangements involve a 3,3-sigmatropic shift. There are reviews providing usefulness of this rearrangement reaction. ... 

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