Rhodium(III)‐Catalyzed Transannulation of Cyclopropenes with N‐Phenoxyacetamides through CH Activation

Abstract

An efficient rhodium(III)-catalyzed synthesis of 2H-chromene from N-phenoxyacetamides and cyclopropenes has been developed. The reaction represents the first example of using cyclopropenes as a three-carbon unit in rhodium(III)-catalyzed C(sp(2))-H activations.

Mechanistic Understanding of the Divergent Reactivity of Cyclopropenes in Rh(III)-Catalyzed C–H Activation/Cycloaddition Reactions of N-Phenoxyacetamide and N-Pivaloxybenzamide

“…6 Recent research from the Wang group disclosed the Rh(III)-catalyzed reactions of N-pivaloxybenzamide (A) and N-phenoxyacetamide (B) with cyclopropenes to give tricyclic lactam P1 and 2H-chromene P2 (Scheme 1a). 7 Thus, interesting substrate-dependent chemoselectivity was uncovered as the three-membered ring of the cyclopropene is retained in reaction with A while ring-opening reaction of cyclopropene occurred with substrate B. 8…”

“…9,10 On the other hand, the β-C elimination from intermediate I, generating an 8-membered rhodacycle likes II, should be favorable by releasing of the ring strain of the cyclopropane moiety. 11 Besides, the ring-opening of cyclopropene by activation of the π bond was implied in literatures, 7,12 whether such a process could compete with the C-H activation under Cp*Rh(III) catalysis is unknown. In addition, while the concept of external oxidant-free C-H activations becomes more and more 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3 popular, 13,14,15 how the O-NHAc moiety in N-phenoxyacetamides works as an internal oxidant is still unclear.…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…1075) formation from the cyclopropene, aryl migration to afford the σ-allyl species (e.g. 1076), allylic rearrangement, and C-O coupling to afford the observed products in the proposed mechanistic pathway [1125]. A rhodium carbene complex (e.g.…”

Rh‐Catalyzed Synthesis of Oxygen‐Containing Heterocycles

“…In 2014, Wang and coworkers discolesed a rhodium(III)-catalyzed annulation of N-phenoxyacetamide with cyclopropenes (Scheme 6.20), which represents the first example of using cyclopropene as a three-carbon unit in rhodium(III)-catalyzed C(sp 2 )-H activation [33]. The reaction proceeded well at room temperature and showed broad substrate scope with respect to both cyclopropenes and N-phenoxyacetamides.…”