Rearrangement of groups

A series of benzofuran derivatives bearing an ester group at the 2-position has been prepared by the irradiation of quinone intermediates. Dihydrobenzofurans have medicinal importance, and the interesting feature of this work is that cyclization occurs with rearrangement of groups, via the spirocyclopropane intermediate (41). 

BUTENE. As shown in Figure 38, a group attached to C-1 can migrate from position 1 to 3 (1,3 shift) to produce an isomer. If it is a methyl group, we recover a 1-butene. If it is a hydrogen atom, 2-butene is obtained. A third possible product is the cyclopropane derivative. The photochemical rearrangement of 1-butene was studied extensively both experimentally [88]... 

The mechanism of the rearrangement catalyzed by Pd(fl), typically by PdCl2(RCN)2, is explained by the oxypalladation of an alkene to form 810 as an intermediate, or cyclization-induced rearrangement. As a limitation, no rearrangement takes place when the allylie ester 812 is substituted at the C-2 position of the allyl group, while a smooth rearrangement of 811 takes place[500]. 

The benzidine-like rearrangement of 2-hydrazinothiazoles has been observed by the Beyer group (523, 546). This rearrangement may be very fast (539). but does not occur with 2.2 -hydrazothiazole (300). where the... 

Because acylation of an aromatic ring can be accomplished without rearrangement it is frequently used as the first step m a procedure for the alkylation of aromatic compounds by acylation-reduction As we saw m Section 12 6 Friedel-Crafts alkylation of ben zene with primary alkyl halides normally yields products having rearranged alkyl groups as substituents When a compound of the type ArCH2R is desired a two step sequence IS used m which the first step is a Friedel-Crafts acylation... 

Diketones and tetraketones derived from aromatic compounds by conversion of two or four SCH groups into keto groups, with any necessary rearrangement of double bonds to a quinonoid structure, are named by adding the suffix -quinone and any necessary affixes. 

Another indole/oxindole synthesis achieves the critical ortho-substitution by Sommelet-Hauser rearrangement of an anilinosiilfonium ion intermediate. Use of P-thioketones (G = R, an alkyl group) generates 2-substituted indoles, whereas P-thioesters (G = OR) lead to oxindoles. In each case, a 3-thio substituent must be removed by desulfuri2ation. 

One of the most useful reactions in forming a P—C bond is the Michaehs-Arbusov reaction, which is a characteristic reaction of tricoordinate phosphoms compounds containing an alkoxy group (22). Alkylation of the electron pair is followed by rearrangement of the initial phosphonium salt. 

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