Potassium teter-butoxide Strikes Again!

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C–H carboxylation of heteroarenes with ambient CO₂

Sabine Fenner^a and   Lutz Ackermann*^a  

Green Chem., 2016, Advance Article

The C–H carboxylation of heteroarenes was achieved under transition metal-free reaction conditions with naturally abundant CO₂ as the C1 source at relatively low temperature. The C–H carboxylation was mediated by KOt-Bu at atmospheric pressure of CO₂, and thereby provided atom- and step-economical access to various heteroaromatic carboxylic acid derivatives.

Mild metal-catalyzed C–H activation: examples and concepts

Mild metal-catalyzed C–H activation: examples and concepts

T. Gensch, M. N. Hopkinson, F. Glorius, and J. Wencel-Delord

Chem. Soc. Rev.

Abstract:

Organic reactions that involve the direct functionalization of non-activated C–H bonds represent an attractive class of transformations which maximize atom- and step-economy, and simplify chemical synthesis. Due to the high stability of C–H bonds, these processes, however, have most often required harsh reaction conditions, which has drastically limited their use as tools for the synthesis of complex organic molecules. Following the increased understanding of mechanistic aspects of C–H activation gained over recent years, great strides have been taken to design and develop new protocols that proceed efficiently under mild conditions and duly benefit from improved functional group tolerance and selectivity. In this review, we present the current state of the art in this field and detail C–H activation transformations reported since 2011 that proceed either at or below ambient temperature, in the absence of strongly acidic or basic additives or without strong oxidants. Furthermore, by identifying and discussing the major strategies that have led to these improvements, we hope that this review will serve as a useful conceptual overview and inspire the next generation of mild C–H transformations.

Silver(I)-Catalyzed Tandem Sigamatropic Rearrangement/1,3‑H Shift/ 6π Aza-electrocyclization of N‑Propargylic Hydrazones: A Mild Synthetic Route to 1,6-Dihydropyridazines

Silver(I)-Catalyzed Tandem Sigamatropic Rearrangement/1,3‑H Shift/ 6 π Aza-electrocyclization of N‑Propargylic Hydrazones: A Mild Synthetic Route to 1,6-Dihydropyridazines

Zong-Cang Ding, Lu-Chuan Ju, Ying Yang, Xiao-Ming An, Yun-Bing Zhou, Ren-Hao Li, Hai-Tao Tang, Cheng-Ke Ding, and Zhuang-Ping Zhan*

 

Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, P. R. China

J. Org. Chem. DOI: 10.1021/acs.joc.6b00428

TOC:

Abstract:

A highly efficient AgOTf catalyzed [3,3]

sigmatropic rearrangement/1,3-H shift/6π aza-electrocycliza-

tion cascade reaction of N-propargylic hydrazones has been

developed. This method provides a new mild synthetic route

to various polysubstituted 1,6-dihydropyridazines including the

3-CF3-substituted ones with high selectivity.

 

Alkyl–Aryl Coupling Catalyzed by Tandem Systems of Pincer-Ligated Iridium Complexes and Zeolites

Long V. Dinh^†, Bo Li^†, Akshai Kumar^†‡, William Schinski^§, Kathleen D. Field^†, Alexander Kuperman^§, Fuat E. Celik^*⊥, and Alan S. Goldman^*†

^† Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, United States

^‡ Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam India

^§ Chevron Energy Technology Company, 100 Chevron Way, Richmond, California 94802, United States

^⊥ Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, United States

ACS Catal., 2016, 6, pp 2836–2841

DOI: 10.1021/acscatal.6b00149

Publication Date (Web): March 28, 2016

Copyright © 2016 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acscatal.6b00149

We report that pincer-ligated iridium catalysts for alkane dehydrogenation can operate in tandem with zeolite catalysts for arene–alkene coupling, to effect the overall intramolecular dehydrocoupling of alkyl–H and aryl–H bonds (i.e., the dehydrocyclization of alkyl benzene). Thus, zeolite and soluble iridium cocatalysts in refluxing pentylbenzene (205 °C) gave high yields of 1-methyl-1,2,3,4-tetrahydronaphthalene. Subsequent dehydrogenation and isomerization affords 1- and 2-methylnaphthalene and 2-methyl-1,2,3,4-tetrahydronaphthalene. Total yields of cyclized product as high as 5.4 M (94%) have been obtained, corresponding to 6800 turnovers per mol Ir. Turnover numbers for the tandem-catalyzed dehydrocyclization are much greater than those obtained for simple dehydrogenation by Ir catalysts (to give olefins) in the absence of zeolite.