Beilstein J. Org. Chem.2017,13, 1866–1870, doi:10.3762/bjoc.13.181
proceeds via base-promoted propargyl–allenyl rearrangement followed by cyclization and allyl migration. Phosphine-substituted indoles can be synthesized by a similar strategy.
Keywords: allyl migration; benzothiophene; indole; metal-free; propargyl-allenyl; Introduction
Heterocycles are frequently found
unstable or reactive polyfunctionalized allene substrates [17][18][19][20][21][22][23][24][25][26][27]. Although transition metal (e.g., Au, Pd)-catalysed propargyl–allenyl isomerization and cyclization reactions have been established [28][29], such transformations promoted by a base to construct
propargyl–allenyl rearrangement [17][18][19][20][21][22][23][24][25][26][27] and an allyl migration [32][33][34] (Scheme 1). In addition, phosphine-substituted indole derivatives could also be conveniently constructed by a similar strategy. This method not only avoids the use of transition metal catalysts
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Graphical Abstract
Figure 1:
Examples of biologically active benzothiophene derivatives.
Beilstein J. Org. Chem.2015,11, 1441–1446, doi:10.3762/bjoc.11.156
support of ab initio and DFT computations, this work shows that observed results can be explained by assuming an exchange equilibrium between energetically close N-propargyl, allenyl and N-alkynyl forms and that the reaction outcome correlates to a particular equilibrium mixture. Due to the very small
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Graphical Abstract
Scheme 1:
Preparation of propargylamides through alkylation of secondary amides and base-catalyzed isomerizat...