Dehydrogenative Cycloisomerization/Arylation Sequence ofN‐Propargyl Carboxamides with Arenes by Iodine(III)‐Catalysis

Abstract

Dehydrogenative cycloisomerization/arylation sequence of heteroatom nucleophile‐tethered unactivated alkynes provides a facile and powerful approach to C−C bond formation between the generated heterocycles and unfunctionalized arenes. Here, we describe a hypervalent iodine(III)‐catalyzed synthesis of oxazoles concomitant with the introduction of aryl groups into side chain from N‐propargyl carboxamides and arenes, representing first C(sp3)−C(sp2) bond formation by the catalytic dehydrogenative cycloisomerization/arylation reaction in exo‐dig modes.

Metal-free electrochemical oxidative intramolecular cyclization ofN-propargylbenzamides: facile access to oxazole ketals

“…Supported by cyclic voltammetry results, control experiments, and previous reports, 5–7,11 we proposed a reasonable reaction mechanism, as shown in Scheme 4. This elegant electrocatalytic 5- exo-dig radical cyclization reaction begins with anodic oxidation of the anion intermediate I formed from the deprotonation of substrate 1a assisted by the cathode produced MeO − to deliver the nitrogen-centered radical intermediate II , followed by isomerization to give the oxygen-centered radical III .…”

“…4 Recent research studies have focused on transition-metal (such as Au, Cu, Pd, Fe, Ag etc .) catalyzed, 5 iodine-promoted, 6 or visible-light-catalyzed 7 intramolecular cyclization reactions of N -propargylamides to construct attractive oxazole skeletons (Scheme 1a). For instance, in 2021, Li et al successfully developed a highly attractive strategy for the intramolecular cyclization reaction to construct alkylated oxazoles by merging Au/Cu catalysis with Cu/photoredox catalysis.…”

Iodine(iii)-catalyzed dehydrogenative cycloisomerization–arylation sequence of 2-propargyl 1,3-dicarbonyl compounds

“…On the basis of the above observations and our previous report on the iodine(III)-mediated oxidative cycloisomerization, 9 we proposed a catalytic cycle for the synthesis of arylated furans 3 from 1 and 2 (Scheme 6). First, the ArI precatalyst is oxidized by sulfinyl fluoride 6b derived from Bn 2 SO and F-TEDA-PF 6 and/or a complex of 6b, Bn 2 O and TEDA-PF 6 .…”

“…The proto-deiodination of β-iodinated enols like INT-B has been known. 9,14 On the other hand, 7 reacts with CAT-A and/or ArIF 2 ( produced by proto-iodination of INT-B) prior to HF to give INT-C (path b′). This process would be partially responsible for the formation of 3.…”

“…On the other hand, as part of our research on the synthesis of heterocycles based on the hypervalent iodine(III)-catalyzed difunctionalization of alkynes, 9 we recently developed a dehydrogenative cycloisomerization-arylation sequence of N-propargyl carboxamides (X = N) with the C(sp 3 )-C(sp 2 ) bond formation (Scheme 1c). 9a Although hypervalent iodine(III) com-pounds have been shown to be effective on the dehydrogenative C-C bond formation, 10 some of which have been advanced to the iodine(III)-catalysis, 11 only a few catalytic intermolecular arylation reactions have been reported.…”