Divergent Reactivity of Rhodium(I) Carbenes Derived from Indole Annulations

Abstract

Rh(I)-carbenes were generated from propargylic alcohol derivatives as the result of a dehydrative indole annulation. Depending on the choice of the electron-withdrawing group on the aniline nitrogen nucleophile, either cyclopropanation product or dimerization product was obtained chemoselectively. Intramolecular hydroamidation occurred for the same type of propargylic alcohol derivatives when other transition metal catalysts were employed.

Fe(III)-Catalyzed Bicyclization of Yne-Allenones With Indoles for the Atom-Economic Synthesis of 3-Indolyl Cyclobutarenes

“…Based on the above experimental observations and literature reports (Haibach et al, 2011; Li et al, 2015, 2018a; Liu et al, 2016, 2017a; Ozaki et al, 2017; Sha et al, 2018b), a feasible mechanism for forming products 3 was proposed in Scheme 3. Initially, the intramolecular [2 + 2] cycloaddition of yne-allenones 1 rapidly occurs to yield cyclobutene intermediate A .…”

“…To continue our efforts in this project (Liu et al, 2017a; Wang J.-Y. et al, 2017; Li et al, 2018a,b; Sha et al, 2018b; Wang et al, 2018), we attempted to employ indoles 2 to be subjected with the reaction of yne-allenones 3 under our previous conditions (Li et al, 2018a) to assemble naphtho[1,2- a ]carbazol-5-ols 4 (Scheme 1d), owing to indoles with C2 and C3 reactive sites could acted as C 2 synthons for the synthesis of fused indoles (Haibach et al, 2011; Li et al, 2015; Liu et al, 2016; Ozaki et al, 2017). Unexpectedly, a double [2 + 2] cycloaddition relay did not occur.…”

One‐pot synthesis of benzimidazole‐pyrazines and their anticancer activities

“…Most of current hydroamination reaction of alkynes involved the usage of transition‐metal catalysts . However, transition‐metal catalysts are usually expensive; moreover, they are very toxic that must be carefully removed from the final products, especially during the synthesis of compounds for human usage.…”

Tandem Annulations of Propargylic Alcohols to Indole Derivatives

“…[27] In 2015, Liu and Tang found the indole annulation of 2-aminophenyl propargylic alcohols 97 could deliver the rhodium(I) carbene 102, which either underwent chemoselectively cyclopropanation or dimerization to form the corresponding products 99 or 101, respectively, depending on the choice of the Nprotecting groups. [28] In the presence of 5 mol% of [{Rh(CO) 2 Cl} 2 ], propargylic alcohols with aryl sulfonyl as the nitrogen protecting group reacted with various styrenes smoothly at room temperature for 12-20 h, affording the cyclopropanation products 99 in moderate to good yields with 5:1-20:1 dr values (Scheme 19). When alkoxy carbonyl or acyl group was A plausible mechanism was proposed to explain the indole annulation/cyclopropanation or dimerization.…”