Chemoselective Oxidative C(CO)C(methyl) Bond Cleavage of Methyl Ketones to Aldehydes Catalyzed by CuI with Molecular Oxygen

Abstract

Aldehyde Termination: A novel copper-catalyzed transformation from methyl ketones into aldehydes has been accomplished. This method is applicable to a wide range of aromatic and aliphatic methyl ketones and chemoselectively produces aldehydes, accompanied by the release of hydrogen (H2 ) and carbon dioxide (CO2 ) as by-products.

Base metal-catalyzed benzylic oxidation of (aryl)(heteroaryl)methanes with molecular oxygen

“…The coupling of 2-arylacetaldehydes with anilines resulting in the formation of 2-aryl-α-ketoacetamides was reported by Jiao [22] and a closely related intramolecular variant leading to isatins has been published by Ilangovan [23]. A remarkable Cu-catalyzed chemoselective oxidative C–C bond cleavage of methyl ketones was reported by the group of Liu and Bi [24]. This useful transformation makes use of CuI/O 2 in DMSO to convert methyl ketones into aldehydes in a sustainable manner.…”

Friedel–Crafts Coupling of Electron-Deficient Benzoylacetones Tuned by Remote Electronic Effects

“…14,15 In the present research, initially, the reactions of 1 bearing a terminal acetyl group were examined with 2-(1,3-dithiolan-2-ylidene)-1-phenylbutane-1,3-dione 1a as a model employing the catalyst system applied to the oxidative C-C bond cleavage reaction of methyl ketones. 12 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 Table 2, a wide range of naphthoquinone derivatives 2 were prepared, which all participated in a straightforward manner for the unusual intramolecular acylation reaction, thereby furnishing the desired naphthoquinones 2 with high efficiency. For the aryl ketone substrates 1 with either electron-donating (1b−1g, 1j, 1k and 1l) or electron-withdrawing substitutes (1h, 1i and 1m) on the aryl ring of 1 gave the corresponding acylation products 2 in good to excellent yields.…”

“…12 Interestingly, under identical reaction conditions, the 1,2-diacylbenzene derivatives, 3-(1,3-dithiolan-2-ylidene)naphthalene-1,2,4(3H)-triones 2 and 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 2-(1,3-dithiolan-2-ylidene)-1H-indene-1,3(2H)-diones 5, were obtained from the reactions of 2-(1,3-dithiolan-2-ylidene)-1-phenylbutane-1,3-diones 1 and 2-(1,3-dithiolan-2-ylidene)-1-phenylpentane-1,3-diones 4, respectively (Scheme 1c). These transformations represent the unusual modes of the Friedel−Crafts reaction involving the C-C bond formation on a benzene ring having a strongly electron-withdrawing acyl group.…”

“…As the results, 3-(1,3-dithiolan-2-ylidene)-1-methylquinoline-2,4(1H,3H)-diones 9a and 9b were obtained in moderate yields (Scheme 2d). Although the Friedel−Crafts-type CDC process for the formation of 9 via aldehyde intermediate 10 can't be excluded, 20 a mechanism involving Friedel−Crafts cyclization 1-5 to form alcohol intermediate 11 followed by aerobic oxidation12,13 to form 9 is preferred due to N-acyl anilines 8 have the electron-rich aromatic ring.Based on the above experimental results, a mechanism for the formation of naphthoquinones 2 is proposed with the reaction of 1a as an example (Scheme 3a). Similar as the previous work, Cu-catalyzed aerobic oxidation of 1a gives aldehyde intermediate I via the enol form of 1a' 12,13,…”

“…tuned to the electron-rich one at this stage by the remote electron-donating enol p- conjugation structure of the side chain.23 As the result of the umpolung of the innate reactivity of aryl ketone 1a at the ortho-position of the aryl ring, the intramolecular Friedel−Crafts reaction of intermediate III enables the formation of naphthoquinone 2a through an intramolecular Friedel−Crafts reaction as the crucial step, followed by deprotonation, regeneration of the catalyst, Cu(OAc) 2 , and Cu(OAc) 2 -catalyzed aerobic oxidation sequence (Scheme 3a) 12,13,[9][10][11] the zwitterionic resonance contribution of III'attributing to an S … O interaction of the -oxo ketene dithioacetal moiety (Scheme 3a) 15,24,25 may play an important role for the remote electronic effects to make the polarity reverse of the electron-deficient aromatic ring to the electron-rich one.…”