7693-50-7Relevant articles and documents
Asymmetric o-to-c aryloxycarbonyl migration of indolyl carbonates using single-handed dynamic helical polyquinoxalines bearing 4-aminopyridyl groups as chiral nucleophilic catalysts
Yamamoto, Takeshi,Takahashi, Takuya,Murakami, Ryo,Ariki, Naoto,Suginome, Michinori
supporting information, p. 943 - 949 (2021/04/29)
Use of single-handed dynamic helical macromolecules as nucleophilic catalysts in asymmetric Steglich-type O-to-C aryloxycarbonyl rearrangement of 3-substituted indol-2-yl aryl carbonates is demonstrated. Among several single-handed poly-(quinoxaline-2,3-diyl) copolymers (PQXap) bearing achiral 4-aminopyridin-3-yl groups at the 5-position of the quinoxaline rings, PQXmdpp and PQXapy, containing N-methylpyrrolidine-fused pyridin-3-yl and 4-(1-azetidinyl)pyridin-3-yl groups, respectively, showed higher enantioselectivity and catalytic activity than PQXdmap, bearing 4-dimethylamino-pyridine-3-yl groups. Substrates bearing p-(trifluoromethyl)phenyloxycarbonyl groups on both the nitrogen and oxygen atoms showed high reactivity, giving oxindoles with a quaternary stereogenic carbon center at their 3-positions in up to 97:3 enantiomeric ratio in THF. The macromolecular catalysts underwent inversion of their helix sense by solvent effect, allowing the same catalyst to give the opposite enantiomer in a mixture of methyl t-butyl ether and 1,1,2-trichloroethane (3:1). The macromolecular catalysts could be easily recovered by adding acetonitrile to the reaction mixture and were reused four times without reduction in enantioselectivity.
β-type glycosidic bond formation by palladium-catalyzed decarboxylative allylation
Xiang, Shaohua,Lu, Zhiqiang,He, Jingxi,Hoang, Kim Le Mai,Zeng, Jing,Liu, Xue-Wei
supporting information, p. 14047 - 14051 (2013/11/19)
The efficient and stereoselective construction of glycosidic linkages is of great significance in carbohydrate chemistry due to the ubiquitous existence of numerous biologically active natural products and saccharides. Although great efforts have been devoted to stereoselective glycosylations in the past few decades, constructing glycosidic bonds with high efficiency and selectivity remains a challenge and continues to be an important area in carbohydrate research. Phenols are widely used as nucleophiles in palladium-catalyzed allylation. In contrast, the possibility of using aliphatic alcohols as nucleophiles is not as thoroughly explored. The modified reaction conditions were then applied to other substrates. Originating from easily prepared carbonates, various glycosides, such as phenolic Oglycosides, thiophenolic S-glycoside, aliphatic O-glycosides, and even disaccharides, were synthesized in good yields by means of a palladium-catalyzed decarboxylative allylation.
Synthesis of polyalkylphenyl prop-2-ynoates and their flash vacuum pyrolysis to polyalkylcyclohepta[b]furan-2(2H)-ones
Nagel, Matthias,Hansen, Hans-Juergen
, p. 1022 - 1048 (2007/10/03)
A new method for the smooth and highly efficient preparation of polyalkylated aryl propiolates has been developed. It is based on the formation of the corresponding aryl carbonochloridates (cf Scheme 1 and Table 1) that react with sodium (or lithium) propiolate in THF at 25-65°, with intermediate generation of the mixed anhydrides of the arylcarbonic acids and prop-2-ynoic acid, which then decompose almost quantitatively into CO2 and the aryl propiolates (cf. Scheme 11). This procedure is superior to the transformation of propynoic acid into its difficult-to-handle acid chloride, which is then reacted with sodium (or lithium) arenolates. A number of the polyalkylated aryl propiolates were subjected to flash vacuum pyrolysis (FVP) at 600-650°and 10-2 Torr which led to the formation of the corresponding cyclohepta[b]furan-2(2H)-ones in average yields of 25-45% (cf. Scheme 14). It has further been found in pilot experiments that the polyalkylated cyclohepta[b]furan-2(2H)-ones react with 1-(pyrrolidin-1-yl)cyclohexene in toluene at 120-130°to yield the corresponding 1,2,3,4- tetrahydrobenz[a]azulenes, which become, with the growing number of Me groups at the seven-membered ring, more and more sensitive to oxidative destruction by air (cf. Scheme 15).
