The Coming of Age in Iodane-Guided ortho-C-H Propargylation: From Insight to Synthetic Potential.
As early as 1991 Ochiai et al. reported that an acid-activated form of phenyliodine diacetate, PhI(OAc)2 , undergoes a reaction with propargyl-silanes, germanes and stannanes to give the ortho-propargyl iodobenzene. This formal C-H alkylation was proposed to take place through an unusual (even to date) iodonio-based [3,3] rearrangement of an intermediate allenylsilane. Although this mechanistic principle has been invoked in related iodane-directed C-H coupling reaction, some underlying principles have remained unaddressed, and the reaction rarely employed. Herein, DFT evidence for a mechanism best described as iodine-guided electrophilic aromatic substitution is presented. Using a newly optimized reaction protocol that significantly reduces the undesired reduction process, the potency of the method is showcased through the synthesis of >40 structurally diverse ortho-iodo propargyl (or allenyl) arenes.
['Izquierdo|Susana|S|http://orcid.org/0000-0002-6608-1910', 'Bouvet|Sébastien|S|http://orcid.org/0000-0003-1039-1570', 'Wu|Yichen|Y|http://orcid.org/0000-0002-0639-0412', 'Molina|Sonia|S|http://orcid.org/0000-0001-7576-146X', 'Shafir|Alexandr|A|http://orcid.org/0000-0002-8127-2299']
C−H functionalization haloarenes hypervalent iodine iodane-directed coupling synthetic methods