A new practical synthesis of triaryl and trisindolylmethanes under solvent-free reaction conditions

Abstract

An efficient and practical synthesis of triaryl and trisindolylmethanes is reported via the bisarylation of aryl aldehydes with activated arenes. The new method features mild solvent-free reaction conditions, in most cases nearly stoichiometric reagent ratios, catalytic amount of the readily available, easily-handled, recoverable and reusable Brønsted acid catalyst o-benzenedisulfonimide.

Highly modulated bisindoles: ligands for copper‐catalyzed Sonogashira reaction

“…In another set of experiments (entries 6, 9-11), the effect of base was examined: K 2 CO 3 was the best choice. Finally, the solvent effect was studied, showing that only in DMF did the reaction proceed smoothly (entries 6, [12][13][14]. The scope and limitation of BIM/Cu catalyst system were extensively explored with functionalized aryl iodides and terminal alkynes ( Table 2).…”

Four‐Component Synthesis of Phosphonium Salts: Application Toward an Alternative Approach to Cross‐Coupling for the Synthesis of Bis‐Heteroarenes

“…In this proposed pathway,the most challenging part would be the generation of phosphonium salt via afour-component reaction. Thec hallenges that needed to be overcome are 1) [2+ +1] adducts could be generated instead of the required phosphonium salt due to competition between arene nucleophile and phosphine towards the aldehyde; [9] 2) nucleophilicity of phosphine would be perturbed to agreat extent by the acid used;and 3) acid could be trapped by phosphine and vice versa, thereby preventing the condensation of arene nucleophile with aldehyde.…”

Four‐Component Synthesis of Phosphonium Salts: Application Toward an Alternative Approach to Cross‐Coupling for the Synthesis of Bis‐Heteroarenes

“…Thec hallenges that needed to be overcome are 1) [2+ +1] adducts could be generated instead of the required phosphonium salt due to competition between arene nucleophile and phosphine towards the aldehyde; [9] 2) nucleophilicity of phosphine would be perturbed to agreat extent by the acid used;and 3) acid could be trapped by phosphine and vice versa, thereby preventing the condensation of arene nucleophile with aldehyde. Thec hallenges that needed to be overcome are 1) [2+ +1] adducts could be generated instead of the required phosphonium salt due to competition between arene nucleophile and phosphine towards the aldehyde; [9] 2) nucleophilicity of phosphine would be perturbed to agreat extent by the acid used;and 3) acid could be trapped by phosphine and vice versa, thereby preventing the condensation of arene nucleophile with aldehyde.…”

“…[10] Thus an ew four-component reaction involving 1a, 2a,p hosphine,a nd acid was discovered. On the other hand, when TfOH and PBu 3 were sequentially added to asolution of 2a in MeCN,followed by 1a,noformation of 3aawas seen, but generation of aldehydeacid-phosphine adduct 4 [12] and [2+ +1] adduct 5 [9] could be observed by 1 Ha nd 31 PNMR analysis (entry 17). Carrying out the reaction in acetonitrile could slightly enhance the rate of reaction (entry 9).…”

“…It was also seen that in cases other than PBu 3 -appended salts, free phosphine was generated during the course of the reaction by decomposition of the salt, thereby reducing the efficiency of acylation/intramolecular Wittig reaction cascade (entries 2-4). Along with the expected adducts,f ormation of 5-10 %o fb is-acylated [c] trace (73) [ 1M e, HH ( 3aa)P h(8a)1 76 (9aaa) [9] 2B n, HH ( 3ba)P h3 81 (9baa) 3 [c] Me, Ph H(3da)P h9 63 (9daa) 4 [c] Me, Me H(3ea)P h9 62 (9eaa) 5M e, H5 -Br (3ab)P h3 99 (9aba) 6M e, H5 -Br p-OMePh (8b)1 92 (9abb) 7M e, H5 -Br p-BrPh (8c)3 84 (9abc) 8M e, H5 -Cl (3ac)P h(8a)1 99 (9aca) 9M e, H5 -Me (3ad)P h3 70 (9ada) 10 Me, H5 -OMe (3ae)P h2 81 (9aea) 11 Me, H4 -OMe (3af)P h4 81 (9afa) 12 Me, H3 -OMe (3ag)P h3 99 (9aga) 13 Me [10] was isolated along with 9aaj. Abrief screening of solvents showed that acetonitrile was the best one (entries 1, 7-10).…”