1226-91-1Relevant academic research and scientific papers
In situ formed acetals facilitated direct Michael addition of unactivated ketones
Koppolu, Srinivasa Rao,Balamurugan, Rengarajan
, p. 1186 - 1192 (2017/02/10)
TfOH-promoted synthesis of 1,5-diketones by the Michael reaction of unactivated ketones with chalcones has been described. Acetals formed under HC(OMe)3/TfOH conditions generate the required enol-equivalents for a smooth Michael reaction. A wide array of symmetrical and unsymmetrical 1,5-diketones has been synthesised.
Development of N,N-bis(perfluoroalkanesulfonyl)squaramides as new strong Br?nsted acids and their application to organic reactions
Cheon, Cheol Hong,Yamamoto, Hisashi
supporting information; experimental part, p. 4257 - 4264 (2010/07/06)
New strong Br?nsted acids derived from a squaric acid scaffold bearing different perfluoroalkanesulfonyl groups have been developed and applied to several organic reactions. These squaramides are bench-stable and exhibit much higher reactivities in several organic reactions than squaric acid itself. N,N-Bis(trifluoromethanesulfonyl)squaramide 2a was applied to the Mukaiyama aldol reaction and Mukaiyama Michael reaction. Mechanistic studies revealed that the Br?nsted acid might be the predominant catalyst through direct protonation of carbonyl compound by the acid itself rather than the silylated Br?nsted acid. The utility of this acid 2a was further extended to Hosomi-Sakurai allylation of aldehydes and a carbonyl-ene reaction. Furthermore, other squaramides 2b and c bearing longer perfluoroalkyl chains have been developed, which are also bench-stable and displayed similar reactivities with squaramide 2a in several organic reactions.
A new Br?nsted acid derived from squaric acid and its application to Mukaiyama aldol and Michael reactions
Cheon, Cheol Hong,Yamamoto, Hisashi
scheme or table, p. 3555 - 3558 (2009/10/26)
Bis-N-trifluoromethanesulfonyl squaramide was prepared as a new bench-stable strong Br?nsted acid and applied to the Br?nsted acid-catalyzed Mukaiyama aldol and Michael reactions with silyl enol ethers. The resulting Mukaiyama aldol products of aldehydes
Michael addition of stannyl ketone enolate to α,β-unsaturated esters catalyzed by tetrabutylammonium bromide and an ab initio theoretical study of the reaction course
Yasuda, Makoto,Chiba, Kouji,Ohigashi, Noriyuki,Katoh, Yasuhiro,Baba, Akio
, p. 7291 - 7300 (2007/10/03)
Michael addition of stannyl ketone enolates to α,β-unsaturated esters was accomplished in the presence of a catalytic amount of tetrabutylammonium bromide (Bu4NBr). Other typical systems using lithium enolate or silyl enolate with catalysts (TiCl4 or Bu4NF) failed to give the desired products. The bromide anion from Bu4NBr coordinates to the tin center in enolate to accelerate the conjugate addition where a five-coordinated tin species was generated. The coordination of the bromide anion significantly raises the HOMO level of tin enolate and enhances its nucleophilicity. The conjugate addition provides the intermediate Michael adduct, which has an ester enolate moiety, and the adduct immediately transforms to α-stannyl γ-ketoester by keto - enol tautomerization. This step contributes to the stabilization of the product system and leads to a thermodynamically favorable reaction course. An ab initio calculation reveals that the activation energy in the reaction using the bromide anion is lower than that of the reaction without using it. The transition state in either reaction course has a linear structure, not a cyclic one. This system can be applied to a variety of tin enolates and α,β-unsaturated carbonyls involving enoates, enones, and unsaturated amides.
Generation of β-Carbonyl Radicals from Cyclopropanol Derivatives by the Oxidation with Manganese(III) 2-Pyridinecarboxylate and Their Reactions with Electron-Rich and -Deficient Olefins
Iwasawa, Nobuharu,Hayakawa, Satoshi,Funahashi, Masahiro,Isobe, Koichi,Narasaka, Koichi
, p. 819 - 827 (2007/10/02)
Various β-carbonyl radicals are generated oxidatively from cyclopropanol derivatives by the use of manganese(III) 2-pyridinecarboxylate (Mn(pic)3).These β-carbonyl radicals react with electron-rich olefins such as conjugated silyl enol ethers, a ketene th
Generation of β-Keto Radicals from Cyclopropanol Derivatives by the Use of Manganese(III) 2-Pyridinecarboxylate as an Oxidant and Their Reactions with Olefins
Iwasawa, Nobuharu,Hayakawa, Satoshi,Isobe, Koichi,Narasaka, Koichi
, p. 1193 - 1196 (2007/10/02)
Various β-keto radicals are generated from cyclopropanol derivates such as 1- or 2-substituted cyclopropanols and a cyclopropanone hemiacetal by the use of manganese(III) 2-pyridinecarboxylate, and their reactions with electron-rich olefins give cross-addition products in good yields.
New role of tin(II) compounds in organic synthesis
Mukaiyama, Teruaki,Kobayashi, Shu
, p. 39 - 52 (2007/10/02)
Three new carbon-carbon bond forming reactions by the use of new catalyst systems involving tin(II) compounds are described in this article.The aldol reaction of silyl enol ethers with acetals or aldehydes and the Michael reaction of silyl enol ethers wit
An Efficient and Convenient Method for the Preparation of α-Methylenated Ketones from Silyl Enol Ethers
Hayashi, Masaji,Mukaiyama, Teruaki
, p. 1283 - 1286 (2007/10/02)
In the presence of a catalytic amount of stannous halide, silyl enol ethers react with bromomethyl methyl ether to give the corresponding α-bromoethyl ketones, which are smoothly converted to α-methylenated ketones on the successive addition of tertiary amine by one-pot procedure.This method is successfully applied to a synthesis of sarkomycin intermediate.
Δ3-DIHYDROPYRANS AND TETRAHYDROPYRANS BY REDUCTION OF PYRYLIUM SALTS WITH SODIUM BOROHYDRIDE IN ACETIC ACID
Balaban, Teodor-Silviu,Balaban, Alexandru, T.
, p. 1341 - 1344 (2007/10/02)
The major reduction products with triacetoxyborohydride (NaBH4 in AcOH) of 2,4,6-trisubstituted pyrylium salts bearing alkyl substituents in the 2- and/or 6-position are the Δ3-dihydropyrans with cis 2- and 6-substituents and all-cis-2,4,6-trisubstituted tetrahydropyrans. Δ3-dihydropyrans are shown to be formed via 2H-pyrans by a 1,4 reduction while tetrahydropyrans result from 4H-pyrans by reduction of both enol-ether double bonds.
