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Organic Lab Reactions 30

Organic Lab Reactions 30 - ether rearranges completely in...

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CONDITIONS OF REARRANGEMENT 25 able -para substitution and disubstitution, and does not give a high yield of a pure product. In the only instance 108a noted in the literature in which an acid catalyst was used to rearrange an allyl phenyl ether, allyl 2-methoxyphenyl ether (LXXIX) rearranged at 78° in the presence of boron fluoride and acetic acid to give 38% of eugenol (LXXX), with guaiacol, 6-allyleugenol, and the allyl ether of allylguaiacol as by- products. When the rearrangement of LXXIX is carried out thermally, OC 3 H 6 OH OH )CH S ' LXXIX LXXXI an excellent yield of LXXXI is obtained (Table I). The presence of acids in the Claisen rearrangement might be disadvantageous because the 2- allylphenols might be isomerized to the heterocyclic compounds (see p. 18). Experience with a variety of allyl ethers has indicated that in general it is not necessary to heat etchers above 200° to effect rearrangement, and that many preparations in the literature probably would give better yields if they were run at lower temperatures. Allyl 4-methylphenyl
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Unformatted text preview: ether rearranges completely in thirteen hours at 200° without solvent, 67 and the corresponding 2,4- and 2,6-dimethyl compounds react more rapidly. The allyl ethers of 2-phenanthrol and 3-phenanthrol rearrange at 100 . 61 Allyl 2-nitrophenyl ether gives a 73% yield after heating five hours at 180°, but the 4-nitro compound rearranges much more^lowly. The allyl ethers of the isomeric hydroxynaphthoquinones (LXXXII and LXXXIII) rearrange in a few minutes at 136-145° to give the same compound (LXXXIV). 84 iOC 3 H B Substitution in the a-or 7-position of the allyl group increases the rate of rearrangement; the crotyl ether of 2,4-dichlorophenol rearranges more rapidly than the allyl ether. 46 a-Ethylcrotyl phenyl ether rear-ranges to the extent of 10% in twenty-four hours at 120°." a-Ethyl-io3« Bryusova and Joffe. J. Gen. Chem. U.S.S.R., 11, 722 (1941) \C. A., 36,430 (1942)1....
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