7661-40-7Relevant academic research and scientific papers
Radical C?H Acylation of Nitrogen Heterocycles Induced by an Aerobic Oxidation of Aldehydes
Paul, Subhasis,Bhakat, Manotosh,Guin, Joyram
supporting information, p. 3154 - 3160 (2019/08/30)
An aerobic radical approach for the synthesis of unsymmetrical heteroaryl ketones is described herein. The reaction involves cross-dehydrogenative coupling between aldehydes and heteroaromatic bases with molecular oxygen (O2). The key aspect of the method is the generation of reactive acyl radical via homolytic activation of aldehyde C?H bond using O2 as the sole oxidant. The reaction has a good substrate scope with respect to aldehydes and functionalized nitrogen heterocycles. Based on our mechanistic studies, a radical chain pathway is suggested for the reaction. A synthetic application of the method is demonstrated in the formal synthesis of natural alkaloid (±) angustureine.
General copper-catalyzed coupling of alkyl-, aryl-, and alkynylaluminum reagents with organohalides
Shrestha, Bijay,Thapa, Surendra,Gurung, Santosh K.,Pike, Ryan A. S.,Giri, Ramesh
, p. 787 - 802 (2016/02/18)
We report the first example of a very general Cu-catalyzed cross-coupling of organoaluminum reagents with organohalides. The reactions proceed for the couplings of alkyl-, aryl-, and alkynylaluminum reagents with aryl and heteroaryl halides and vinyl bromides, affording the cross-coupled products in good to excellent yields. Both primary and secondary alkylaluminum reagents can be utilized as organometallic coupling partners. These reactions are not complicated by β-hydride elimination, and as a result rearranged products are not observed with secondary alkylaluminum reagents even for couplings with heteroaryl halides under "ligand-free" conditions. Radical clock experiment with a radical probe and relative reactivity study of Ph3Al with two haloarenes, 1-bromonaphthalene and 4-chlorobenzonitrile, having two different redox potentials indicates that the reaction does not involve free aryl radicals and radical anions as intermediates. These results combined with the result of the Hammett plot obtained by reacting Ph3Al with iodoarenes containing p-H, p-Me, p-F, and p-CF3 substituents, which shows a linear curve (R2 = 0.99) with a ρ value of +1.06, suggest that the current transformation follows an oxidative addition-reductive elimination pathway.
Alcohols as alkylating agents in heteroarene C-H functionalization
Jin, Jian,MacMillan, David W. C.
, p. 87 - 90 (2015/09/15)
Redox processes and radical intermediates are found in many biochemical processes, including deoxyribonucleotide synthesis and oxidative DNA damage. One of the core principles underlying DNA biosynthesis is the radical-mediated elimination of H2O to deoxygenate ribonucleotides, an example of 'spin-centre shift', during which an alcohol C-O bond is cleaved, resulting in a carbon-centred radical intermediate. Although spin-centre shift is a well-understood biochemical process, it is underused by the synthetic organic chemistry community. We wondered whether it would be possible to take advantage of this naturally occurring process to accomplish mild, non-traditional alkylation reactions using alcohols as radical precursors. Because conventional radical-based alkylation methods require the use of stoichiometric oxidants, increased temperatures or peroxides, a mild protocol using simple and abundant alkylating agents would have considerable use in the synthesis of diversely functionalized pharmacophores. Here we describe the development of a dual catalytic alkylation of heteroarenes, using alcohols as mild alkylating reagents. This method represents the first, to our knowledge, broadly applicable use of unactivated alcohols as latent alkylating reagents, achieved via the successful merger of photoredox and hydrogen atom transfer catalysis. The value of this multi-catalytic protocol has been demonstrated through the late-stage functionalization of the medicinal agents, fasudil and milrinone.
