- Dual C(sp3)-H Functionalization of Cyclic Ethers via Singlet Oxygen-Mediated Ring Opening and Ring Closing
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A metal-free dual C(sp3)-H bond functionalization of saturated cyclic ethers via photooxidative singlet oxygen-mediated ring opening and ring closing has been developed, providing a method for generating hydrobenzofurans/pyrans/dioxins. Mechanistic studies have confirmed that ring-opening intermediates were effectively generated by singlet oxygen-mediated C(sp3)-H activation and efficiently reacted with aldehydes and activated methylene compounds to form a wide array of products with high diastereoselectivities (up to >95:5 dr). This study is a rare example of α,β-dual C(sp3)-H bond functionalization of ethers.
- Yuan, Xu,Yu, Xianglin,He, Kun,Zhang, Ruihan,Xiao, Weilie,Lin, Jun,Zhan, Zhajun,Cheng, Xiaohong,Shao, Zhihui,Jin, Yi
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supporting information
p. 8267 - 8272
(2021/10/25)
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- Enantioselective Copper-Catalyzed Radical Ring-Opening Cyanation of Cyclopropanols and Cyclopropanone Acetals
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A novel approach for enantioselective cyanation of cyclopropanols and their derivatives through copper-catalyzed radical relay processes has been developed. Various cyclopropanols and cyclopropanone acetals are compatible to the catalytic conditions, providing β-carbonyl nitriles with excellent enantioselectivity. These products can be readily converted to chiral γ-amino acids derivatives and drugs such as (R)-baclofen. Preliminary mechanistic studies have supported a ring-opening process for cyclopropanoxy radicals followed by copper-catalyzed enantioselective cyanation of benzylic radicals to form the C?CN bonds in an enantioselective manner. (Figure presented.).
- Chen, Pinghong,Guo, Yin-Long,Liu, Guosheng,Wang, Lei,Wu, Lianqian
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p. 2189 - 2194
(2020/04/17)
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- In Situ Generated Magnesium Cyanide as an Efficient Reagent for Nucleophilic Cyanation of Nitrosoalkenes and Parent Nitronates
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In situ generated magnesium cyanide [NaCN/Mg(ClO4)2] is suggested as a convenient, readily available, non-volatile and organic-soluble reagent for hydrocyanation reactions. It was successfully used for nucleophilic cyanation of nitrosoalkenes, nitronates, as well as other typical π-electrophiles, such as imines, α,β-unsaturated ketones, alkylidenemalonates and azoalkenes.
- Ushakov, Pavel Yu.,Tabolin, Andrey A.,Ioffe, Sema L.,Sukhorukov, Alexey Yu.
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supporting information
p. 1888 - 1892
(2019/01/30)
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- Facile synthesis of cyanofurans via Michael-addition/cyclization of ene-yne-ketones with trimethylsilyl cyanide
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We have developed a Michael-addition/cyclization procedure between ene-yne-ketones and TMSCN under metal-free conditions. A wide range of cyanofurans was delivered in high yields, which could be further transformed to a series of furo-furanimines, furo-pyridazines or carboxamido-furans. In addition, deuterium-labeling experiments have been conducted to clarify the reaction pathway.
- Yu, Yue,Chen, Yang,Wu, Wanqing,Jiang, Huanfeng
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p. 640 - 643
(2017/01/13)
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- Oxidative conversion of α,α-disubstituted acetamides to corresponding one-carbon-shorter ketones using hypervalent iodine (λ5) reagents in combination with tetraethylammonium bromide
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(Chemical Equation Presented) α,α-Disubstituted acetamides undergo oxidative dehomologation to give one-carbon-shorter ketones when reacted with a hypervalent iodine (λ5) reagent in combination with tetraethylammonium bromide (TEAB) in various solvents. In further studies, one such combination of a hypervalent iodine (λ5) reagent, o-iodoxybenzoic acid, and TEAB has been established as a new, mild, efficient, and general method for the transformation.
- Bellale, Eknath V.,Bhalerao, Dinesh S.,Akamanchi, Krishnacharya G.
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supporting information; experimental part
p. 9473 - 9475
(2009/04/06)
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- An efficient conjugate hydrocyanation of chalcones and related enones with TMSCN under solvent- and additive-free microwave conditions
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A first example of solvent- and additive-free 1,4-addition reaction of α,β-unsaturated ketones such as chalcones, 3-nonen-2-one and benzalacetone with trimethylsilyl cyanide (TMSCN) is described. The addition of TMSCN to chalcones, 3-nonen-2-one, and benzalacetone under microwave irradiation in the absence of Lewis or Br?nsted acids and solvents, yielded the corresponding β-cyanoketones in good to moderate yields, as quite rapidly as in 5 min. No systematic substituent effect of chalcones on the yields was observed. No reaction of α,β-unsaturated esters such as methyl cinnamate with TMSCN took place under the same conditions.
- Iida, Hirokazu,Moromizato, Tatsuya,Hamana, Hiroshi,Matsumoto, Kiyoshi
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p. 2037 - 2039
(2007/10/03)
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- Formaldehyde dialkylhydrazones as neutral formyl anion and cyanide equivalents: Nucleophilic addition to conjugated enones
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A versatile methodology for the nucleophihc formylation and cyanation of conjugated enones is reported. The procedure is based on the use of formaldehyde dimethylhydrazone, which, acting as a neutral formyl anion equivalent, adds to preformed trialkylsilyl-enone complexes. Both 4-(silyl- oxy)-3-enal hydrazones 3 or deprotected 4-oxo aldehyde monohydrazones 4 can be obtained at products depending on quenching conditions. In full analogy, an asymmetric version of the reaction using chiral formaldehyde SAMP- hydrazone as a neutral synthon of the chiral formyl anion has been developed, giving rise to the corresponding adducts 5 and 6 in good yields and with excellent diastereoselectivities (de 85-≤98%). Ozonolysis or HCl-mediated hydrolysis of adducts 4 and 6 readily affords racemic and optically enriched 4-oxo aldehydes 7, respectively. Additionally, high-yielding MMPP-oxidative cleavage of 4-oxo hydrazones 4 and 6 has been performed to obtain 4-oxo nitriles 8 in racemic and optically enriched forms, respectively. In this way, interesting chiral bifunctional building blocks, some of them bearing newly created stereogenic quaternary centers, have been efficiently synthesized.
- Diez,Fernandez,Gasch,Lassaletta,Llera,Martin-Zamora,Vazquez
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p. 5144 - 5155
(2007/10/03)
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- A Novel Acetonylation of Carbonucleophiles via Palladium-Catalyzed Allylation with Isopropyl 2-Methylene-3,5-dioxahexyl Carbonate
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Carbonucleophiles such as malonate esters, β-keto esters, phenylacetate ester, and phenylacetonitrile were acetonylated in high yields by allylation with isopropyl (or methyl) 2-methylene-3,5-dioxahexyl carbonate (4b or 4a) in the presence of palladium-phosphine catalyst under neutral conditions, followed by acidic hydrolysis.Adopting this procedure dihydrojasmone (7) was prepared from ethyl 3-oxononanoate (6) in an overall yield of 72percent.
- Ikeda, Isao,Gu, Xue-Ping,Okuhara, Toshio,Okahara, Mitsuo
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