Ciaisen rearrangement

The (partial) description of the synthesis and coupling of the five fragments starts with the cyclohexyl moiety C —C. The first step involved the enantio- and diastereoselective harpless epoxidation of l,4-pentadien-3-ol described on p. 126f. The epoxide was converted in four steps to a d-vinyl d-lactone which gave a 3-cyclohexenecarboxylate via Ireland-CIaisen rearrangement (cf. p. 87). Uncatalysed hydroboration and oxidation (cf. p. 131) yielded the desired trans-2-methoxycyclohexanol which was protected as a silyl ether. The methyl car-... 

N-chlorosuccinimide, reaction+PhOH, 92 chrysene, bromination of, 405 —, hydrogen exchange with, 258 —, nitration of, 39 cinnamic acid, nitration of, 39 cinnanyl p-totyl ethers, Ciaisen rearrangement of, 472... 

The Claisen rearrangement of allyloxy heterocycles is another reaction which has been studied in some detail. Yields can be variable and mixtures of N- and C-allyl products are sometimes obtained (e.g. equation 70). In other cases the reaction can be of considerable synthetic utility (e.g. equation 71). The thio-CIaisen rearrangement has also been studied in many cases the intermediate thiones react further (equation 72), although they can also be trapped, for example with ethyl chloroformate. 

Geminal Doubly Branched-Chain Sugars by Eschenmoser-Ciaisen Rearrangement U57]... 

Modifications of the Ciaisen rearrangement have been widely used in a variety of synthetic chemistry reactions [85] (O Scheme 18). 

The simple Ciaisen rearrangement itself has been employed in the transformation of the vinylglycal 95 into carbocyclic compounds [86] (O Scheme 19). On heating at 240 °C in o-dichlorobenzene in a sealed tube for 1 h, the desired rearrangement of 95 proceeds in the... 

T. Tsunoda and co-workers synthesized the antipode of naturai antibiotic antimycin Asb starting from (R)-(+)-methyibenzyiamine and utiiizing the asymmetric aza-Ciaisen rearrangement. The amide precursor was deprotonated with LiHMDS at iow temperature then the reaction mixture was refluxed for several hours to bring about the sigmatropic rearrangement. 

Hiii, R. K., Giiman, N. W. Nitrogen anaiog of the Ciaisen rearrangement. Tetrahedron Lett. 1967,1421-1423. 

Padwa, A., Cohen, L. A. Aza-Ciaisen rearrangements in the 2-aiiyioxy substituted oxazoie system. Tetrahedron Lett. 1982, 23, 915-918. 

Nubbemeyer, U. Diastereoseiective Zwitterionic Aza-Ciaisen Rearrangement The Synthesis of Bicyciic Tetrahydrofurans and a Totai Synthesis of (+)-Dihydrocanadensoiide. J. Org. Chem. 1996, 61, 3677-3686. 

A third alternative may also be conceived, if for a moment one disregards all the nonparticipant atoms in compound IV. What is left is just an allyl—vinyl amine, a molecular combination reminiscent of what is necessary to perform a Claisen-type rearrangement (see Problem 19). Application of this rationale to intermediate IV would lead to cis structure in in a smooth, concerted fashion. This transformation is known in the literature as the amino-CIaisen rearrange-... 

Thio-CUttsen rearrangement. Introduction of a side chain to the a-position of chiral bicyclic thiolactams via a thio-CIaisen rearrangement at room temperature is effected with assistance of (MeCN)2PdCl2-... 

Anionic oxy-Ciaisen rearrangement. Ihe [3,31 Claisen rearrangement of en-rdates of a-allyloxy ketones is markedly dependent on the nature of the metal hydride used, and to a less extent, the solvent. An example is the learrangcmeni of a-(allyloxy)propiophcnonc (t) to the a-hydioxy ketone 2. The rearrangement... 

Nitrogen compounds have also been used in aza-CIaisen rearrangement reactions (also see the aza-Cope rearrangement in sec. 11.12.C.iii). 33,478 jn jie generic reaction, heating N-allylic enamines leads to an imine, which could be hydrolyzed to an aldehyde or converted to another nitrogen-containing moiety. 

Chemicai ampiification positive resists based on Ciaisen rearrangement... 

Amine-CIaisen rearrangements of the enaminone salts 479, prepared in situ from the tertiary amines 478, give moderate yields of the hexahydroiso-quinolines 480, Scheme 130 (77TL4299 79JOC124). The procedure was claimed to offer advantages for the preparation of highly functionalized hydroisoquinolines and was also used in the preparation of hydrophenan-thridines (Section VI,G). 

H. H. Baer and Z. S. Hanna, The preparation of amino sugars and branched-chain sugars by palladium-catalysed allylic substitution of alkyl hex-2-enopyranosides. Can. 7. Chem. 59 889 (1981). D. P. Curran, An approach to the enantiocontrolled synthesis of pseudomonic acids via a novel mon-CIaisen rearrangement. Tetrahedron Lett. 23 4309 (1982). 

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