Condensation reactions Cope rearrangement

Entry 6 is analogous to a silyl ketene acetal rearrangement. The reactant in this case is an imide. Entry 7 is an example of PdCl2-catalyzed imidate rearrangement. Entry 8 is an example of an azonia-Cope rearrangement, with the monocylic intermediate then undergoing an intramolecular Mannich condensation. (See Section 2.2.1 for a discussion of the Mannich reaction). Entry 9 shows a thioimidate rearrangement. 

MgS04, the tetracycles 2-648 were obtained with excellent diastereoselectivity in reasonable yield. The reaction presumably starts with a condensation of the aldehydes 2-645 with the benzyl-protected amine moiety of 2-644 to give an iminium ion which can subsequently cyclize to afford the spirocyclic intermediates 2-646. A [3,3] sigmatropic Cope rearrangement then forms the nine-membered cyclic enamines 2-647 which, after protonation, act as the starting point for another indole iminium cyclization to provide the tetracycles 2-648 via 2-647. 

Sheradsky has found that the hydroxyl function of a ketoxime such as acetophenone oxime can be made to react with DMAD when the reaction is carried out in methanol with a basic catalyst, to give mixture of the fumarate and maleate isomers (164) in the ratio 2 1. This mixture on heating undergoes a hetero-Cope rearrangement followed by cyclization and dehydration to give dimethyl 5-phenylpyrrole-2,3-dicarboxylate (168) (Scheme 25). Similarly, Heindel and Chun have reported that vinyl ether adducts (171), obtained by the condensation of arylamide oximes with DMAD, get thermally converted into oxa-diazolines (172) or imidazolinones (174), depending on the reaction conditions. A similar reaction occurs with aromatic amidoxime-methyl propiolate adducts to give imidazoles (170) (Scheme 26). 1,2,4-Dioxazoles have been reported to be formed in the reaction of hydrox-amic acids with DMAD. - ... 

C-H activation-Cope rearrangement, 10, 177 Claisen condensation equivalent, 10, 174 Claisen rearrangement equivalent, 10, 176 enolate alkylation equivalent, 10, 171 Mannich reaction equivalent, 10, 174 as strategic reaction, 10, 171 intermolecular C-H insertion, C-H activation-Cope rearrangement as strategic reaction, 10, 178... 

From two conjugated carbonyl compounds the cross-benzoin condensation initiated by a chiral azolecarbene (199) sets up a sequence of oxy-Cope rearrangement, aldol reaction and decarboxylation/ ... 

Homologation-condensation. The reaction of cyclic p-keto esters with a vinylmagnesium halide also triggers oxy-Cope rearrangement and Claisen condensation. Bridged ring compounds can be prepared by this method. ... 

Blechert et developed a multicomponent cascade reaction for the synthesis of indole derivatives as depicted in Scheme 1.8.5.17. The first step of the sequence involves formation of a nitrone derivative starting from phenylhydroxylamines and aldehydes. The resulting nitrones were not isolated but captured by a cyanoallene in a 1,3-dipolar cycloaddition reaction followed by hetero-Cope rearrangement, ring-opening and condensation to yield an indole derivative. 

The Overman pyrrolidine synthesis is a tandem reaction, or cascade, used to generate acylpyrrolidine derivatives. This process begins with condensation of an allylic alcohol/ether-containing secondary homoallylic amine with an aldehyde, followed by an aza-Cope rearrangement and subsequent Mannich reaction. Commonly, this reaction is run in refluxing benzene with an acidic additive, such as c/-10-camphorsulfonic acid (CSA). 

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