Copper‐Catalyzed Oxidative CO Coupling by Direct CH Bond Activation of Formamides: Synthesis of Enol Carbamates and 2‐Carbonyl‐Substituted Phenol Carbamates

Abstract

Formamide CH bond activation has been achieved under oxidative conditions, using a copper catalyst and tert‐butyl hydroperoxide (TBHP) as the external oxidant (see scheme). This oxidative coupling of a range of dialkyl formamides provides an easy, phosgene‐free route for the selective synthesis of Z‐enol carbamates and 2‐carbonyl‐substituted phenol carbamates in high yields.

Cu-MOFs as active, selective and reusable catalysts for oxidative C–O bond coupling reactions by direct C–H activation of formamides, aldehydes and ethers

“…In line with the results reported earlier by Kumar et al, 3 reaction of benzaldehyde and 2-hydroxyacetophenone in the presence of copper acetate (5 mol%) and TBHP yields 80% of the corresponding ester, 5, after about 1.5 h (entry 2, …”

“…The reaction was proposed to proceed through the formation of a formamide radical species, as shown in Scheme 2. Kumar et al also demonstrated that both -keto esters (a') and 2-carbonyl-substituted phenols (b') can be coupled with either aldehydes (b) 3 or ethers (c) 5 , leading respectively to phenol esters (b-b' ) or ethers (c-b') and unsymmetrical acetals (c-a'), also implying in both cases a direct activation of a C-H bond of either an aldehyde (b) or a -C-H bond of an ether (c) (see Scheme 1).…”

“…In this sense, Kumar et al 3 and Barve et al 4 , have recently shown that various copper salts can catalyze the oxidative C-O coupling reaction of dialkyl formamides (a)…”

Metal-Free Csp3–N Bond Cleavage of Amides Using tert-Butyl Hydroperoxide as Oxidant

“…This reaction system has been reported to proceed in the present of a copper catalyst. 12 Initially, ethyl 3-oxo-3-phenylpropanoate and DMF were chosen as the model substrates to optimize the reaction conditions. As summarized in Table 1, the reaction gave a trace amount of the desired product without catalyst using K 2 S 2 O 8 as the oxidant at 100 °C for 24 h under a nitrogen atmosphere ( Table 1, entry 1).…”

Cu(OAc)2·H2O-Promoted Tandem β-Alkynyl Elimination of α- or β-Hydroxy Propargylic Alcohols and Homocoupling of the Resulting Alkynyl Species

“…9 I then undergoes C(sp)-C(sp 3 ) bond cleavage via β-alkynyl elimination to form intermediate II with release of 2. Intermediate II then decomposes into phenylacetylene radicals and CuOAc.…”