75-97-8Relevant articles and documents
Pocker,Ronald
, p. 3122,3123,3124 (1978)
The role of SET in the deprotection of (thio)ketals under photosensitization by π-acceptors
Fasani, Elisa,Freccero, Mauro,Mella, Mariella,Albini, Angelo
, p. 2219 - 2232 (1997)
Efficient deprotection of 2-methyl-2-tert-butyl-1,3-dithiolane and of the corresponding oxathiolane to give the ketone is obtained by photosensitization by a catalytic amount of aromatic nitriles (benzenetetracarbonitrile, TCB, and antracenedicarbonitrile, DCA the latter only in the presence of biphenyl) or of heterocyclic salts (triphenylpyrylium tetrafluoborate, TPPT, and methylacridinium perchlorate, MAP), in oxygen saturated solutions. The reaction involves SET to the excited π-acceptor and interception of the substrate radical cation either by oxygen (in the case of the heterocyclics) or by the superoxide anion (in the case of the nitriles). Triplet chloranil (Chl) acts both as oxidant and as proton acceptor, and thus deprotection is accompanied by formation of a stoichiometric amount of the hydroquinone ChlH2. The corresponding dioxolane is a weaker donor: SET occurs only with photoexcited TCB and causes C-C bond fragmentation, not deprotection. The other π-acceptors photosensitize the deprotection of the dioxolane, but in this case they act as Lewis acids (Chl gives a trimer under this condition). This method is unsatisfactory with protected aldehydes. The different reactivity of the radical cations of thioketals and of ketals and the scope of this deprotection method are discussed.
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Badertscher,Whitmore
, (1933)
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Kyung,J.H.,Clapp,L.B.
, p. 2024 - 2027 (1976)
Catalytic Acceptorless Dehydrogenation of Aliphatic Alcohols
Fuse, Hiromu,Mitsunuma, Harunobu,Kanai, Motomu
supporting information, p. 4493 - 4499 (2020/03/05)
We developed the first acceptorless dehydrogenation of aliphatic secondary alcohols to ketones under visible light irradiation at room temperature by devising a ternary hybrid catalyst system comprising a photoredox catalyst, a thiophosphate organocatalyst, and a nickel catalyst. The reaction proceeded through three main steps: hydrogen atom transfer from the α-C-H bond of an alcohol substrate to the thiyl radical of the photo-oxidized organocatalyst, interception of the generated carbon-centered radical with a nickel catalyst, and β-hydride elimination. The reaction proceeded in high yield under mild conditions without producing side products (except H2 gas) from various alcohols, including sterically hindered alcohols, a steroid, and a pharmaceutical derivative. This catalyst system also promoted acceptorless cross-dehydrogenative esterification from aldehydes and alcohols through hemiacetal intermediates.
Catalytic conversion of ketones to esters: Via C(O)-C bond cleavage under transition-metal free conditions
Subaramanian, Murugan,Ramar, Palmurukan M.,Rana, Jagannath,Gupta, Virendra Kumar,Balaraman, Ekambaram
supporting information, p. 8143 - 8146 (2020/09/09)
The catalytic conversion of ketones to esters via C(O)-C bond cleavage under transition-metal free conditions is reported. This catalytic process proceeds under solvent-free conditions and offers an easy operational procedure, broad substrate scope with excellent selectivity, and reaction scalability. This journal is