Claisen rearrangements defined

The eighth volume of this serial publication comprises eight contributions from international authors. Four of these deal with well-defined groups of compounds thiopyrones (R. Zahradnik, R. Mayer, and W. Broy), phenoxazines and phenothiazines (M. Ionescu and H. Mantsch), diazepines (F. D. Popp and A. Catala Noble), and benz-isoxazoles (anthranils and indoxazenes) (K.-H. Wiinsch and A. J. Boulton). J. M. Tedder has surveyed the field of the heteroaromatic diazo compounds which are derived from a variety of heterocyclic ring systems, and M. Schulz and K. Kirschke discuss heterocyclic peroxides. The remaining two chapters survey well-known reactions the Hilbert-Johnson reaction is covered by J. Pliml and M. PrystaS, and heterocyclic Claisen rearrangements by B. S. Thyagarajan. 

Among the most favorable features of the Carroll variant of the Claisen rearrangement are the relative ease of preparation of the parent system by condensation of allylic alcohols with acetoacetic estet or di-ketene and the defined configuration of the intermediately generated double bond. The Carroll rearrange-... 

Chorismate mutase provides an example of an enzyme where QM/MM calculations have identified an important catalytic principle at work [8], This enzyme catalyses the Claisen rearrangement of chorismate to prephenate. The reaction within the enzyme is not believed to involve chemical catalysis, and this pericylic reaction also occurs readily in solution. Lyne et al. [8] investigated the reaction in chorismate mutase in QM/MM calculations, at the AMI QM level (AMI was found to perform acceptably well for this reaction in comparisons with ab initio results for the reaction in the gas phase [8]). Different sizes of QM system were tested in the QM/MM studies (e.g. including the substrate and no, or up to three, protein side chains), and similar results found in all cases. The reaction was modelled by minimization along an approximate reaction coordinate, defined as the ratio of the forming C-C and breaking C-0 bonds. Values of the reaction coordinate were taken from the AMI intrinsic reaction coordinate for the gas-phase reaction. 

W-Alkyl-A -allyl enamines 128 (X = NR), like their carbon and oxygen counterparts 128 (X = CH2,0), can undergo [3,3]-sigmatropic rearrangement to form y,<5-unsaturated imines 129 (X = NR) (equation 27). This reaction has been defined as a 3-aza-Cope or the aliphatic amino-Claisen rearrangement. ... 

The Carroll rearrangement, first reported in 1940210-212, is an old and well-established versatile yet complementary variant of the Claisen rearrangement. The mechanism of this reaction was proposed in 1943 by Kimel and Cope213. With respect to the stereoselectivity, the most favorable feature of the Carroll rearrangement is the defined configuration of the double bond generated in the intermediate hydrogen-bonded enol. 

For [3,3] sigmatropic reactions such as the Claisen rearrangement, reference to well-defined, energetically distinct conformations of the cyclohexane system forms the basis of a self-consistent and highly intuitive transition state model for the electrocyclic event, from which stereo- ... 

The Claisen rearrangement, a heteroatomic variant of the Cope process, holds equal appeal as a scaffolding element that is totally atom-efficient. We have addressed and defined those stereocontrol elements associated with a two-carbon intercalation tactic [55] in several contexts as, for example, in the preparation of (-f)-ceroplastol I (101) [56]. 

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