Cobalt‐Catalyzed Cross‐Coupling of Organozinc Halides with Bromoalkynes

Abstract

The cobalt-catalyzed cross-coupling of organozinc bromides is described. In the case of arylzinc reagents, the same cobalt catalyst, CoBr 2

Reductive Decarboxylative Alkynylation of N‐Hydroxyphthalimide Esters with Bromoalkynes

“…First, the high reactivity of bromoalkynes could pose a selectivity problem. [9] Second, the low steric bulk of the alkyne could lead to rapid transmetalation and homocoupling to form diynes. Finally, alkynes can act as radical acceptors and strong ligands, potentially leading to catalyst inhibition and side reactions.…”

Transition‐Metal‐Catalyzed Electrophilic Amination: Application of O‐Benzoylhydroxylamines in the Construction of the C−N Bond

“…In 2014, Gosmini et al reported as hort review on the recent advances in electrophilica mination reactions, includingp art of the R 2 NÀOBz involvedr eactions. [11] However, the electrophilic aminationr eaction, in particular, those using of O-benzoylhydroxylamines as amination reagents, has developed rapidly, and several breakthroughsh ave been achieved recently.T hus it is necessary to update the new advances in this field. Herein, we would like to contributeacomprehensive review focusing on transitionmetal-catalyzed electrophilic amination reactions using R 2 NÀ OBz as the electrophilica minating reagent.…”

Decarboxylative Negishi Coupling of Redox‐Active Aliphatic Esters by Cobalt Catalysis

“…The success of an in situ activation protocol and the facile synthesis of the drug molecule (AE)-preclamol highlight the synthetic potential of this method. [8] Inspired by these elegant studies,w e reasoned that al ow-valent cobalt catalyst could also donate an electron to the redox-active ester, [9] thereby triggering alkyl radical formation and af ollow-up cross-coupling reaction.Cobalt, as an earth-abundant and low-toxic first-row transition metal, has been previously identified as an attrac-tive catalyst enabling the effective coupling of aryl, [10] alkenyl, [11] and alkynyl halides [12] (or their pseudohalides) with organozinc compounds (Figure 1a). [1] While organohalides have enjoyed as uccess as the electrophilic coupling partners,r ecent years have witnessed ag rowing interest in the use of aliphatic carboxylic acids (or their derivatives) as alkyl halide surrogates in such reactions.…”

“…Cobalt, as an earth-abundant and low-toxic first-row transition metal, has been previously identified as an attrac-tive catalyst enabling the effective coupling of aryl, [10] alkenyl, [11] and alkynyl halides [12] (or their pseudohalides) with organozinc compounds (Figure 1a). Nevertheless,t he use of unactivated alkyl electrophiles [13] in cobalt-catalyzed Negishi coupling reactions is only recent.…”

“…[15] Theu se of the tetrachloro-substituted NHPI ester TCNHP was also effective,b ut resulted in lower yield (44 %). Besides p-toluenesulfonyl (Ts), other commonly encountered amino protecting groups,s uch as benzoyl (Bz;p roducts 4,8,10,12), carboxybenzyl (Cbz; products 5, 13), and tert-butoxycarbonyl (Boc;products 6, 26) were compatible.O ther heterocyclic (products 24-27)a nd cyclic secondary carboxylic acids (product 28), including those bearing an a-heteroatom (products 26, 27), were all viable substrates.I nterestingly,N -protected phenylalanine could also be used to deliver the corresponding product 29. Anumber of ligands were screened, but no improvement in the yield was observed.…”