REACTIVITY OF 3,6-DIMETHOXY-3,6-DIMETHYLCYCLOHEXA-1,4-DIENE - NUCLEAR VERSUS BENZYLIC NUCLEOPHILIC-SUBSTITUTION

被引:15
作者
ALONSO, F [1 ]
BARBA, I [1 ]
YUS, M [1 ]
机构
[1] UNIV ALICANTE,FAC CIENCIAS,DIV QUIM ORGAN,E-03690 ALICANTE,SPAIN
关键词
D O I
10.1016/S0040-4020(01)89773-8
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
The treatment of cis/trans-3,6-dimethoxy-3,6-dimethylcyclo-hexa-1, 4-diene (ca. 1/1 mixture; easily prepared electrochemically in multigram scale from p-xylene) under acidic conditions (acetic, trifluoroacetic, sulfuric, or a Lewis acid) yields almost exclusively 2-methoxy-1,4-dimethylbenzene 4, through a transposition reaction. The use of aqueous hydrochloric or hydrofluoric acid gives 2,5-di-methylphenol 12, and with hydrogen chloride a mixture of 2- and α- chloro-P-xylene (13, 14) is isolated. Different oxygen-, nitrogen-, and sulfur-containing nucleophiles (alcohols, thiols, or hydrazoic acid) react with 3 under acid catalysis giving the corresponding products resulting from a nuclear or/and benzylic substitution on P-xylene (15-20). The reaction of compound 3 with organolithium reagents affords exclusively benzylic products 21 in a regiospecific manner. In all cases the mixtures of isomers are separated by column chromatography. The lithiation of compound 3 with lithium powder or lithium naphthalenide fails, giving P-xylene. A probable mechanism is proposed for the studied reactions. © 1990.
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页码:2069 / 2080
页数:12
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