Organopromoted direct synthesis of 6-iodo-3-methylthioimidazo[1,2-a]pyridines via convergent integration of three self-sorting domino sequences

Abstract

An NH2CN-promoted convergent integration of three self-sorting domino sequences is described for the construction of 6-iodo-3-methylthioimidazo[1,2-a]pyridines from aryl methyl ketones and 2-aminopyridines. This strategy allows the construction of an imidazo[1,2-a]pyridine ring along with methylthiolation at C-3 and iodination at C-6. Preliminary mechanistic studies indicate that this process terminates at the iodination stage without Kornblum oxidation in the presence of I2 and DMSO.

Oxidative Thioesterification of Alkenes Mediated by 1,3‐Dibromo‐5,5‐dimethylhydantoin and DMSO for the Synthesis of α‐Ketothioesters

“…Based on the above results and previous literatures, a possible mechanism is depicted as shown in Scheme . First, styrene 1a reacts with DBH to generate the bromonium ion A , which undergoes regioselective ring opening and eliminates Me 2 S to afford 2‐bromoacetophenone 3 in the presence of DMSO.…”

Transition‐Metal‐Free Oxidative Cross‐Coupling of Methylhetarenes with Imidazoheterocycles towards Efficient C(sp2)−H Carbonylation

“…Both 1a and 2a were treated with molecular iodine (1 equiv) in DMSO,a nd the reactionc onditions werev aried as summarized in Table 1. To our delight, the desired product 3a was obtained in 65 %y ield along with minor methylthiolated byproduct 4 [17] when the reactionw as performed at 100 8C ( Table 1, entry 1).…”

Regioselective, Solvent‐ and Metal‐Free Chalcogenation of Imidazo[1,2‐a]pyridines by Employing I2/DMSO as the Catalytic Oxidation System

“…With regardt ot he influence of the oxidanto nt he selenylation of substrate 1a,wefound that the use of H 2 O 2 or TBHP instead of DMSO resulted in al esse fficient transformation (Table 1, entries [14][15][16][17][18][19]. The use of DMSO (3 mL) as the solvent did not providea ny further positive influence on the yield of 3a (entry 16 vs. 12).…”

“…These results indicate that scavenging the generated HI terminates the catalytic cycle by inhibiting the DMSO activation. To exclude the unusual formation of C−I and C−S bonds with imidazo[1,2‐ a ]‐pyridines, we carried out an experiment without diphenyl diselenide ( 2 a ). Interestingly, we did not observe these unusual products; we believe that this is the consequence of a low concentration of iodine and DMSO (Scheme e).…”