Copper-catalyzed enantioselective diyne cyclizationviaC(sp²)–O bond cleavage

Abstract

The functionalization of etheric C–O bonds via C–O bond cleavage is an attractive strategy for the construction of C–C and C–X bonds in organic synthesis. However, these reactions mainly involve...

Copper-catalyzed intermolecular formal (5 + 1) annulation of 1,5-diynes with 1,2,5-oxadiazoles

“…Plausible reaction mechanism. On the basis of the above experimental results and our previous study on the copper-catalyzed cyclization of N-propargyl ynamides [38][39][40][41][42][43][44][45][46][47] , a plausible reaction mechanism to rationalize the formation of pyrrole-substituted oxadiazine 3a is shown in Fig. 6.…”

“…Screening of reaction conditions. To prohibit the background C-H insertion reaction 38 , 2,6-dimethylphenyl-substituted Npropargyl ynamide 1a was first chosen as the model substrate to react with 1,2,5-oxadiazole 2a under our previous related reaction conditions [38][39][40][41][42][43][44][45][46][47] , and selected results are listed in Table 1. To our delight, the expected 1,2,5-oxadiazine 3a was indeed formed in 37% yield in the presence of 10 mol % of CuOTf as catalyst (Table 1, entry 1).…”

“…In the past decade, the chemistry of vinyl cations has received particular attention because of their unique carbene-like reactivity 36,37 . Recently, our group reported a copper-catalyzed diyne cyclization via vinyl cations as key intermediates, providing a variety of polycyclic pyrrole derivatives [38][39][40][41][42][43][44][45][46][47] . In particular, the related catalytic asymmetric transformations were established via a remote control of enantioselectivity.…”

Enantioselective functionalization of unactivated C(sp3)–H bonds through copper-catalyzed diyne cyclization by kinetic resolution

“…To prohibit the background aromatic C–H insertion reaction 56 , 2,6-dimethylphenyl-substituted N -propargyl ynamide 1a was chosen as the model substrate under our previous related reaction conditions 56 – 62 , and selected results are listed in Table 1 . First, some typical chiral biphosphine ligands and bisoxazoline (BOX) ligands were employed as chiral ligands in the presence of 10 mol % of Cu(MeCN) 4 PF 6 as the catalyst and 12 mol % of NaBAr F 4 as the additive.…”

“…To our best knowledge, metal-catalyzed asymmetric C(sp 3 )–H insertion via vinyl cations has not been explored yet. Inspired by our recent studies on the chiral copper(I)-catalyzed diyne cyclization via vinyl cations 56 – 62 and the application of ynamides in N-heterocycle synthesis 63 – 70 , we envisioned that copper-catalyzed cyclization of alkyl-substituted N -propargyl ynamides might generate the highly reactive vinyl cation intermediates, which could serve as the equivalent of donor-donor carbenes, and undergo an intramolecular [1,5]-H migration, eventually leading to the enantioenriched pyrrole derivatives and diynes through kinetic resolution. Here we describe the realization of such a chiral copper-catalyzed tandem diyne cyclization/unactivated C(sp 3 )–H insertion reaction (Fig.…”