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β‐substitution of simple pyrroles in metal‐assisted reactions with kthyl diazoacetate
Author(s) -
Maryanoff Bruce E.
Publication year - 1977
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570140140
Subject(s) - chemistry , ethyl diazoacetate , copper , pyrrole , catalysis , transition metal , polymer chemistry , metal , ethyl acetate , reaction conditions , medicinal chemistry , organic chemistry , cyclopropanation
The reaction of N ‐methylpyrrole with ethyl diazoaeelate, assisted by copper bronze or copper powder, as described previously by a number of researchers, produces not only ethyl N ‐melhylpyrrole‐2‐acetate ( 3 ), but also heretofore unrecognized ethyl N ‐melhylpyrrole‐3‐acetate ( 4 ); the ratio of 3/4 was ca. 84/16. Promotion of this reaction with other transition metal catalysts furnished differing proportions of 3 and 4 , indicating that the metal is intimately involved in the substitution process. Certain agents, notably cupric fluoborate, cupric trifluoromelhylsullonate, palladous acetate, and (π‐ C 3 H 5 PdCI ) 2 , were particularly active in this reaction and gave β‐substi‐lulion to the extent of ca. 35‐45%. Other pyrrole compounds, namely 1,2‐dimethylpyrrole, 1,3‐dimethylpyrrole, 3 , and pyrrole, were also found (in preliminary work) to undergo β‐substi‐tution in their reaction with copper carbenoids.