Abstract
The TfOH-mediated reactions of 2,4-diaryl-1,1,1-trifluorobut-3-yn-2-oles (CF3-substituted diaryl propargyl alcohols) with arenes in CH2Cl2 afford 1,3-diaryl-1-CF3-indenes in yields up to 84%. This new process for synthesis of such CF3-indenes is complete at room temperature within one hour. The synthetic potential, scope, and limitations of this reaction were illustrated by more than 70 examples. The proposed reaction mechanism invokes the formation of highly reactive CF3-propargyl cation intermediates that can be trapped at the two mesomeric positions by the intermolecular nucleophilic attack of an arene partner with a subsequent intramolecular ring closure.
Highlights
Acetylene compounds are of great importance for chemistry, biology, medicine, materials science, and other fields of science and technology [1–11]
Based on the electrophilic activation of unsaturated compounds [36], we undertook a special study on the transformation of trifluoromethyl-substituted propargyl alcohols
Summarizing the data obtained on the TfOH-promoted reactions of CF3-propargyl alcohols 1 with different arenes, leading to CF3-indenes (Tables 3–7), one may conclude that these indenes may be formed in several reaction pathways (Scheme 1), depending on the structures of the starting alcohol 1 and the nucleophilicity of the arene
Summary
Acetylene compounds are of great importance for chemistry, biology, medicine, materials science, and other fields of science and technology [1–11]. Among the variety of acetylene compounds, propargyl alcohols play an important role in the synthesis of miscellaneous substances. They have been widely used in Friedel-Crafts alkylation catalyzed by Brønsted [17–23] or Lewis [24–35] acids. Based on our work on the electrophilic activation of unsaturated compounds (alkynes, alkenes, allenes) [36], we undertook a special study on the transformation of Molecules 2018, 23, 3079; doi:10.3390/molecules23123079 www.mdpi.com/journal/molecules. Based on the electrophilic activation of unsaturated compounds (alkynes, alkenes, allenes) [36], we undertook a special study on the transformation of trifluoromethyl-substituted propargyl alcohols. The main goal of this work was to investigate reactions of 2,4-diaryl-1,1,1trifluoromethyl-substituted propargyl alcohols. A desilylation stage (see synthetic procedures in the Supplementary Materials)
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