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1‐Methyl‐5‐(trifluoromethyl)azafulvenium Methide, an Intermediate That Undergoes Reaction through “Unusual” cis ‐ exo ‐1,3‐ and trans ‐ exo ‐1,7‐Cycloadditions
Author(s) -
Peláez Walter José,
Pepino Ana Julieta,
Argüello Gustavo Alejandro,
Pinho e Melo Teresa M. V. D.
Publication year - 2014
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201301922
Subject(s) - chemistry , trifluoromethyl , cycloaddition , quinone methide , photochemistry , medicinal chemistry , stereochemistry , organic chemistry , catalysis , alkyl , quinone
Abstract The generation and reactivity of a new 1‐methyl‐5‐(trifluoromethyl)azafulvenium methide are described. Under microwave‐induced pyrolysis conditions this intermediate could be trapped by dipolarophiles, acting either as a 4π or as an 8π dipole. Quantum chemical calculations carried out at the DFT level of theory allowed the rationalization of the results observed in the cycloaddition of 1‐methyl‐5‐(trifluoromethyl)azafulvenium methide and N ‐substituted maleimides. The study revealed that for 1,7‐cycloadducts the major products are obtained in the trans configuration through the unusual exo ‐cycloaddition mode, whereas for 1,3‐cycloadducts the cis counterparts are obtained from this unexpected approach. In addition, under flash vacuum pyrolysis or conventional thermolysis conditions 1‐methyl‐5‐(trifluoromethyl)azafulvenium methide undergoes an allowed suprafacial sigmatropic [1,8]H shift leading to the formation of 2‐methyl‐3‐(trifluoromethyl)‐1‐vinyl‐1 H ‐pyrrole.