- Hypervalent Iodine Oxidation of 5-Substituted and 5-Methyl-4-substituted Pyrazol-3(2H)-ones. A Facile Synthesis of 2-Alkynoic and 2,3-Allenic Esters
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PhI(OAc)2-MeOH causes oxidation of 5-substituted pyrazol-3(2H)-ones to the 2-alkynoic methyl ester and 5-methyl-4-substituted pyrazol-3(2H)-ones to the 2,3-allenic methyl ester.
- Moriarty, Robert M.,Vaid, Radhe K.,Farid, Payman
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- Hypervalent Iodine Oxidation of 5-Substituted and 4,5-Disubstituted Pyrazol-3(2H)-ones: A Facile Synthesis of Methyl-2-alkynoates and Methyl 2,3-alkadienoates
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Hypervalent iodine oxidation of various 5-substituted pyrazol-3(2H)-ones (1a-h) with iodobenzene diacetate or iodosobenzene in methanol results in fragmentative loss of molecular dinitrogen to yield methyl 2-alkynoates (2a-h).However, 5-methyl-4-substituted pyrazol-3(2H)-ones (3a-d) under similar conditions yield methyl 2,3-allenic esters (4a-d).Methyl 2,3-cycloalkadienoates (6a-e) are obtained by the oxidative cleavage of 4,5-polymethylene pyrazol-3(2H)-ones (5c-e) using iodobenzene diacetate or iodosobenzene in methanol. 5-Methyl-4,4-disubstituted pyrazol-3(2H)-ones (7a-b) were found not to undergo raction under similar conditions.The scope and mechanism of these reactions are discussed.
- Moriarty, R. M.,Vaid, R. K.,Ravikumar, V. T.,Hopkins, T. E.,Farid, P.
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- Synthesis of Spirobidihydropyrazole through Double 1,3-Dipolar Cycloaddition of Nitrilimines with Allenoates
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The double 1,3-dipolar cycloaddition of allenoates with nitrilimines has been achieved under mild reaction conditions, affording a variety of spirobidihydropyrazoles in moderate to excellent yields with excellent diastereoselectivities. The reaction diastereoselectively constructs double dihydropyrazole moieties and two chiral centers including a spiro carbon center.
- Liu, Honglei,Jia, Hao,Wang, Bo,Xiao, Yumei,Guo, Hongchao
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supporting information
p. 4714 - 4717
(2017/09/23)
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- Multicomponent cascade cycloaddition involving tropone, allenoate, and isocyanide: A rapid access to a 7,6,5-fused tricyclic skeleton
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Multicomponent cascade cycloaddition of tropone, allenoate, and isocyanide has been disclosed. This method allows for the rapid construction of a highly unusual tricyclic skeleton in an efficient manner. The proposed transformation proceeds through [8 + 2 + 1] cycloaddition, [1,5]-H shift, and cyclization followed by an alkoxy group migration process.
- Jia, Shuanglong,Su, Shikuan,Li, Chunju,Jia, Xueshun,Li, Jian
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supporting information
p. 5604 - 5607
(2015/02/19)
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- Cycloadditions, XX, Thermally Induced Intramolecular Reactions of 2-Methyl-2,3-butadienamides
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The 2-methyl-2,3-butadienamides 4a-m are directly synthesized by the reaction of the corresponding allenic acid chloride 2 with the secondary amines 3.At heating, 4a-j undergo the intramolecular Diels-Alder reaction, by using their ω-standing double bond and the ?-system of the directly bonded phenyl groups or of the "methylenic" bonded arenes of furans.Thereby the tricycles 6a-g (bearing five-membered lactam moieties) and/or the tricycles 7-9 (bearing six-membered lactam moieties) are formed.The influence of the geminal methyl group on the chemoselectivity and on the velocity of the IMDA reactions is investigated.The N-allyl derivatives of 4 (s. 4l and m) form the bicycles 10 by intramolecular -Cycloaddition. Key words: 2-Methyl-2,3-butadienamides, Intramolecular - and -Cycloadditions
- Himbert,Gerhard,Schlindwein, Hans-Juergen
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p. 1785 - 1794
(2007/10/02)
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