Rearrangement of Benzyl Ethers to Carbinols by Potassium Amide. Mechanism of Isomerization of Carbanions Involving 1,2-Shifts^1,2,3

Abstract

REARRANGEMENT OF BENZYL ETHERS TO CARBINOLS 1437TABLE I1 ANALYSIS OF SAPONIFIED POLYMERS FOR CARBOXYL -COOH Softening Max. in Ester:styr. Sol. of point of M. e. of m. e. sapon. ratio in polymer original -COOH/g. of polypolymer, in CaHs, poljmer, of sapon. -COOH mer, moles NEWARK, DELAWARE (14) J. E. Waltz and G.The objective of this investigation was to establish the mechanism of intramolecular isomerizations of carbanions involving 1,a-shifts of alkyl groups without their bonding pair of electrons. These isomerizations, which include the Stevens rearrangement of quaternary ammonium and sulfonium ions by bases and the Wittig rearrangement of benzyl ethers by lithium phenyl, are to be distinguished from the common rearrangements of carbonium ions in which alkyl groups shift with their bonding pair of electrons. The work of Wittig was extended using lithium butyl and particularly potassium amide with which there can be no doubt that carbanions are actually the intermediates. The relative ease of isomerization of the carbanions of several ethers was established. The carbanion of dibenzyl ether not only isomerized to form the anion of benzylphenylcarbinol but also underwent partly @-elimination to form benzaldehyde and benzyl ion-a type of reaction that predominated with the carbanion of dibenzohydryl ether. These isomerizations as well as those reported previously are in agreement with an internal displacement mechanism.

Mechanistic evidence of a Gabriel Colman-type rearrangement

“…In summary, we present in this work a series of chemical evidences indicating that the alkoxide promoted rearrangement of quinolinimidoacetic acid derivatives (1) leading to a mixture of hydroxy-1,6-and 1,7-naphthyridinones (2,3) goes through a two step mechanism with quinolinamic ester intermediates (4,5).…”

“…In the second mechanism, alkoxide acts as a base generating a carbanion which in an intramolecular attack to imide carbonyl would lead to an intermediate with a three-membered ring (IV). 5 Rapid bond rearrangement of this strained cyclic intermediate would yield the final product.…”

Nucleophilic Amination of Methoxy Arenes Promoted by a Sodium Hydride/Iodide Composite

“…Zuschriften aza- [1,2]-Wittig rearrangement [16] via deprotonation of the benzylic methylene moiety to form ring-expanded 44 or 47, respectively.A lternatively,a nother aza- [1,2]-Wittig rearrangement could be proposed from benzylsodium II to forge an ew CÀCb ond to generate sodium amide III,w hich cyclizes to give 44 or 47.M eanwhile,a lkane 48 might be formed through fragmentation of benzylsodium II (n = 2). [17,18] Several experimental observations provided clues about the reaction mechanism of the present nucleophilic amination of methoxy arenes,w hich is unlikely to proceed through either addition-elimination via the Meisenheimer complex (from electron-rich substrates 15-17)orelimination-addition via the benzyne species (from 2,6-disubstituted substrates 20 and 21). We conducted DFT calculations [19] to investigate the mechanism of the formation of N-methyl tetrahydroquinoline as the model reaction (Figure 1).…”

The ERC Mechanism and the Formation of Abnormal Product in the Stevens Rearrangement

“…For more than a decade various workers [1][2][3][4] have done several projects to determine the mechanism of the Stevens Rearrangement.…”