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Gold‐Catalyzed Bicyclic and [3+2]‐Annulations of Internal Propargyl Alcohols with Nitrones and Imines To Yield to Two Distinct Heterocycles
Author(s) -
More Sayaji Arjun,
Chao TzuHsuan,
Cheng MuJeng,
Liu RaiShung
Publication year - 2021
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.202001119
Subject(s) - chemistry , annulation , bicyclic molecule , catalysis , yield (engineering) , propargyl , cycloisomerization , combinatorial chemistry , medicinal chemistry , stereochemistry , organic chemistry , metallurgy , materials science
Abstract A gold‐catalyzed synthesis of 1,3‐dihydrooxazolo[3,4‐ a ]indoles from 1‐oxo‐3‐yn‐4‐ols and nitrones is described; this new bicyclic annulation presents the first examples that internal alkynes can react with nitrones to undergo an oxoarylation route. DFT calculations indicate a [3,3]‐sigmatropic shift of initial alkenylgold intermediates to elude the intermediacy of gold carbenes. We also developed new [3+2]‐annulations of the same 1‐oxo‐3‐yn‐4‐ols with imines, yielding oxazolidin‐4‐ylidene derivatives efficiently. The tethered alcohols of these 1‐oxo‐3‐ynes allow trapping of their metastable 2‐azadienium intermediates to enable a novel annulation. Our mechanistic analysis indicates that the two products, despite their structural relevance, are produced from two independent systems.