- DMSO as a C1 Source for [2 + 2 + 1] Pyrazole Ring Construction via Metal-Free Annulation with Enaminones and Hydrazines
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A cascade reaction between enaminones, hydrazines, and dimethyl sulfoxide (DMSO) for the synthesis of 1,4-disubstituted pyrazoles catalyzed by molecular iodine in the presence of Selectfluor has been realized. DMSO plays a dual role as the C1 source and the reaction medium. In addition, the synthesis of 1,3,4-trisubstituted pyrazoles using aldehydes as alternative C1 building blocks has also been achieved.
- Guo, Haijin,Tian, Lihong,Liu, Yunyun,Wan, Jie-Ping
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supporting information
p. 228 - 233
(2022/01/04)
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- Reversed-polarity synthesis of diaryl ketones via palladium-catalyzed cross-coupling of acylsilanes
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Acylsilanes serve as acyl anion equivalents in a palladium-catalyzed cross-coupling reaction with aryl bromides to give unsymmetrical diaryl ketones. Water plays a unique and crucial activating role in these reactions. High-throughput experimentation techniques provided successful reaction conditions initially involving phosphites as ligands. Ultimately, 1,3,5,7-tetramethyl-6-phenyl-2,4,8-trioxa-6-phosphaadamantane was identified as giving a longer-lived catalyst with higher turnover numbers. Its use, in conjunction with a palladacycle precatalyst, led to optimal reaction rates and yields. Scope and limitations of this novel method are presented along with initial mechanistic insight.
- Schmink, Jason R.,Krska, Shane W.
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supporting information; experimental part
p. 19574 - 19577
(2012/01/13)
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- Synthesis of new benzylic ethers of oximes derived from 1-phenyl- pyrazole compounds
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In the scope of a research program aiming at the synthesis and pharmacological evaluation of new antithrombotic agents via rational molecular design, we describe in this paper the synthesis of benzyl ethers of aryl-pyrazolic oxime derivatives. Ethers' (2a-2c) and (3a-3c) are derived from 4-formyl-1-N-phenylpyrazole (4) in good yield. Designed as interphenylenic analogues of the ridogrel (1), one expects these compounds to present dual properties, i.e., thromboxane A2 receptors antagonism and thromboxane synthetase inhibition.
- Muri, Estela M. F.,Barreiro, Eliezer J.,Fraga, Carlos A. M.
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p. 1299 - 1321
(2007/10/03)
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- SYNTHESIS AND REACTION OF TRIBUTYLSTANNYLPYRAZOLES
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1,3-Dipolar cycloaddition reaction of diazomethane and ethyl diazoacetate with tributylstannylacetylenes occurred regioselectively to afford the corresponding 3(5)-tributylstannylpyrazoles.The cycloaddition reaction of 3-phenylsydnone with the stannylacetylenes proceeded also regioselectively, and 3-tributylstannyl-1-phenylpyrazoles were isolated. 4-Tributylstannyl- and 5-tributylstannyl-1-phenylpyrazole were prepared by the stannylation of 4-lithio- and 5-lithio-1-phenylpyrazoles with tributylstannyl chloride.Iodination, benzoylation, and phenylation of the stannylpyrazoles were examined.
- Sakamoto, Takao,Shiga, Futoshi,Uchiyama, Daishi,Kondo, Yoshinori,Yamanaka, Hiroshi
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p. 813 - 818
(2007/10/02)
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