- A Unified Catalytic Asymmetric (4+1) and (5+1) Annulation Strategy to Access Chiral Spirooxindole-Fused Oxacycles
-
A unified catalytic asymmetric (N+1) (N=4, 5) annulation reaction of oxindoles with bifunctional peroxides has been achieved in the presence of a chiral phase-transfer catalyst (PTC). This general strategy utilizes peroxides as unique bielectrophilic four- or five-atom synthons to participate in the C?C and the subsequent umpolung C?O bond-forming reactions with one-carbon unit nucleophiles, thus providing a distinct method to access the valuable chiral spirooxindole-tetrahydrofurans and -tetrahydropyrans with good yields and high enantioselectivities under mild conditions. DFT calculations were performed to rationalize the origin of high enantioselectivity. The gram-scale syntheses and synthetic utility of the resultant products were also demonstrated.
- Gao, Min,Gong, Xiangnan,Hu, Lin,Luo, Yanshu,Xia, Yuanzhi,Xu, Qianlan,Zhao, Yukun
-
supporting information
p. 19813 - 19820
(2021/08/03)
-
- α-Carboxy-β-lactones from photoinduced ring contraction of 3-diazodihydrofuran-2,4-diones
-
β-Lactones were prepared by irradiation of 3-diazodihydrofuran-2,4- diones via Wolff rearrangement proceeding with retention of the configuration of the migrating carbon atom. In the presence of alcohols or thiols, but not amines, the corresponding 3-(alkoxycarbonyl)- or 3-[(alkylsulfanyl)carbonyl]- β-lactones were obtained. 5-Alkyl-3-diazodihydrofuran-2,4-diones gave exclusively trans-3,4-disubstituted β-lactones. Georg Thieme Verlag Stuttgart · New York.
- Beneke, Julia,Schobert, Rainer
-
supporting information
p. 773 - 776
(2013/04/10)
-
- A short biomimetic approach to the fully functionalized bicyclic framework of type A acylphloroglucinols
-
A biomimetic approach toward type A polyprenylated acylphlorogluclnols (PPAPs) Is described. The method Is based on a C-alkylation-cation cyclization reaction sequence, leading to a convenient buildup of molecular complexity, employing the simple and read
- Couladouros, Elias A.,Dakanali, Marianna,Demadis, Konstantinos D.,Vidali, Veroniki P.
-
supporting information; experimental part
p. 4430 - 4433
(2009/12/24)
-
- Substituent Effects on the C-C Bond Strength, 19. Geminal Substituent Effects, 10. Radical Stabilization Enthalpies of α,α-Bis(methoxycarbonyl)alkyl and Tris(methoxycarbonyl)methyl Radicals
-
Heats of formation ΔH0f(g) were determined from enthalpies of combustion ΔH0f(c) and enthalpies of vaporization ΔH0vap or sublimation ΔH0sub for the eight substituted methanetricarboxylates 2a-h.From these data and from previously determined enthalpies of formation ΔH0f of substituted malonic esters new thermochemical group increments were derived.From these increments and from the recently published improved increments for carboxylic acid esters the gem. interaction enthalpies of two and three COOR groups were calculated.The radical stabilization enthalpies RSE of α,α-bis(methoxycarbonyl)alkyl (18.2 kJ mol-1, 1a) and tris(methoxycarbonyl)methyl radicals (5.2 kJ mol-1, 1b) were derived from kinetic data obtained by means of our previously developed protocol.They were corrected for the gem. interaction energies of the ester groups in the ground state and are satisfactorily explained by an additive stabilizing effect for the ester substituents and by dipolar substituent interactions in the radicals.The dipolar energies were taken from MM2 calculations. - Keywords: Enthalpies of formation / Geminal substituents, energetic interaction of / Bond cleavage, C-C, kinetics of / Radicals, stabilization of / Increments, thermochemical, of esters
- Rakus, Klaus,Verevkin, Sergey P.,Keller, Manfred,Beckhaus, Hans-Dieter,Ruechardt, Christoph
-
p. 1483 - 1494
(2007/10/02)
-
- Novel pyrrolinone dyes
-
Pyrrolinone dyes, and photographic materials containing them, which dyes have the formula: wherein;, E1 represents an electron withdrawing group;, R1 represents an aryl group of 6 to 14 carbon atoms or an alkyl group of from 1 to 12 carbon atoms;, R2 repr
- -
-
-
- An integrated approach to the synthesis of continguously substituted xanthopurpurins, pachybasins and purpurins
-
Alkylation, hydroxyalkylation and acylation of 3-methyl-, 3-methoxy- and 3,4-dimethoxycrotonates can be induced to occur exclusively in the α-position. Conversion of the products to dienes then provides, through cycloaddition, a wide variety of substitution patterns. This approach is illustrated by simplified syntheses of a number of naturally occurring quinones and confirms the structures proposed for vismiaquinone C, 7-geranylemodin, cinnalutein, 4,5-dihydroxydigitolutein, 2-hydroxyislandicin 1-methyl ether and calyculatone 1-methyl ether.
- Caron,Brassard
-
p. 771 - 784
(2007/10/02)
-
- Enzymes in organic synthesis 51. Probing the dimensions of the large hydrophobic pocket of the active site of pig liver esterase
-
The dimensions of the large hydrophobic pocket (H(L)) of the active site model of pig liver esterase (PLE) were probed using a series of aliphatic and phenylic malonates. Results from the hydrolyses of these new unnatural substrates permitted the extension of the H(L) pocket to give the new dimensions of 6.2 x 2.3 x 3.9 A for a total volume of ~56 A3.
- Provencher,Wynn,Jones,Krawczyk
-
p. 2025 - 2026
(2007/10/02)
-
- ELECTROCHEMICAL CYCLIZATION OF TETRAMETHYL ESTERS OF 2-SUBSTITUTED PROPANE-1,1,3,3-TETRACARBOXYLIC ACIDS IN THE PRESENCE OF SALTS OF HYDROHALIC ACIDS
-
The chemical and electrochemical cyclization of tetramethyl esters of 2-substituted propane-1,1,3,3-tetracarboxylic acids in the presence of hydrohylic acid salt mediators were studied.It was found that the chemical variant of the cyclization of the corresponding α,α'-dianions of esters of propane-1,1,3,3-tetracarboxylic acids by the action of iodine or bromine is substantially inferior to the electrochemical variant.In the latter case, the esters of substituted cyclopropane-1,1,3,3-tetracarboxylic acids are formed in a 87-98percent yield.The tetramethyl ester of 2-isopropylpropane-1,1,3,3-tetracarboxylic acid, which under the electrolysis conditions decomposes according to a Michael retroreaction is an exception.
- Elinson, M. N.,Fedukovich, S. K.,Nikishin, G. I.
-
p. 2523 - 2529
(2007/10/02)
-