Substitution electrophilic, in furans

Electrophilic substitution in furan, thiophene, selenophene and pyrrole has, up to 1970, been comprehensively reviewed by Marino.66 Italian workers have determined the relative reactivities of selenophene and thiophene as well67 relative rates are given in Table I. Including furan, the order of reactivity is furan > selenophene > thiophene. 

Marino, J. 1973. Quantitative effect of electrophilic substitution in furan, thiophene, pyrrole and other five-membered heteroaromatic systems. Khim Geterocicl 5 579-589. 

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