S-functionalized internal olefins, that is, α-oxo ketene dithioacetals, was efficiently achieved with alcohols as the alkoxylating agents, (diacetoxyiodo)benzene (PhI(OAc)2) as the oxidant, and benzoquinone (BQ) as the co-oxidant. The alkoxylated olefins were thus constructed and applied for the synthesis of alkoxylated N-heterocycles. Polarization of the olefinic carbon-carbon doublebond by the electron-donating
Copper-Catalyzed Trifluoromethylation of Internal Olefinic CH Bonds: Efficient Routes to Trifluoromethylated Tetrasubstituted Olefins and N-Heterocycles
olefins has been a challenging task in organic synthesis. Efficient CuII‐catalyzed trifluoromethylation of internal olefins, that is, α‐oxoketene dithioacetals, has been achieved by using Cu(OH)2 as a catalyst and TMSCF3 as a trifluoromethylating reagent. The push–pull effect from the polarized olefin substrates facilitates the internal olefinic CHtrifluoromethylation. Cyclic and acyclic dithioalkyl α‐oxoketene
Synthesis of Methyl 5-Aryl-3-oxo-4-pentenoates and Novel Substituted Cyclopentenones
作者:C. V. Asokan、S. Bhattacharji、H. Ila、H. Junjappa
DOI:10.1055/s-1988-27543
日期:——
The cinnamoyl- (1a-j) and (5-phenyl-2,4-pentadienoyl)- (1k) ketene dithioacetals are shown to undergo methanolysis in the presence of ether-boron trifluoride complex and mercury(II) chloride to the corresponding methyl 5-aryl-3-oxo-4-pentenoates 2a-j and 3-oxo-7-phenyl- 4,6-heptadienoate (2k), respectively, in good yields. However, the corresponding (2-methylcinnamoyl)ketene dithioacetals 3a-f, under identical reaction conditions, undergo Nazarov cyclization to give the corresponding substituted cyclopentenones 4a-f.
α-acylketene dithioacetals in refluxing benzene affords α-acetoxyketene dithioacetals as major products which could be hydrolyzed to α-diketone dithioacetals under mild alkaline conditions. Under similar oxidative conditions, α-cinnamoyl ketene dithioacetals yield 2-acetoxycyclopentenone derivatives through an interesting oxidative Nazarov cyclization involving intermediate α-acetoxy dithioacetals accompanied
S-acetals) under mild conditions. Simple treatment of such enaminones with PhI(OAc)2 at ambient temperature in air afforded diverse multiply functionalized α,β-unsaturatedamides including β-cyclopropylated acrylamides, in which a wide array of functional groups such as aryl, (hetero)aryl, alkenyl, and alkyl can be conveniently introduced to a ketene moiety. The reaction mechanism was investigated by exploring