Abstract DBU-CH3I has been poised to be a substitute for diazomethane in the preparation of methy... more Abstract DBU-CH3I has been poised to be a substitute for diazomethane in the preparation of methyl esters from carboxylic acids. The reactions can be carried out in commercial untreated acetone and acetonitrile, which have been exemplified with several methyl ...
DBU catalyzed condensation of phthalaldehydic acids and 1,3-diketones has been developed to be a ... more DBU catalyzed condensation of phthalaldehydic acids and 1,3-diketones has been developed to be a general method for the synthesis of 3-substituted phthalides. This method, in combination with mercuric acetate mediated oxidative aromatization has been utilized for the regiospecific synthesis of isopestacin (9) and cryphonectric acid (10).
The preparation of the title compounds is accomplished with high (E)-stereoselectivity where only... more The preparation of the title compounds is accomplished with high (E)-stereoselectivity where only elemental sulfur is lost.
A new catalyst Ti(IV)-salan system efficiently promotes the diastereo- and enantioselective monoe... more A new catalyst Ti(IV)-salan system efficiently promotes the diastereo- and enantioselective monoepoxidation of conjugated dienes using H2O2 even in the presence of other olefins and adjacent stereocenters.
Enantiomerically enriched vinyl epoxides offer enticing synthetic versatility and also occur as l... more Enantiomerically enriched vinyl epoxides offer enticing synthetic versatility and also occur as labile metabolites in many biosynthetic pathways of medicinal significance. Herein, we describe an efficient, highly stereo- and regiospecific mono-epoxidation of conjugated dienols using a Ti(IV) catalyst and hydrogen peroxide at rt.
Ti(IV)-salan 4 catalyzes the diastereo-and enantioselective monoepoxidation of conjugated dienes ... more Ti(IV)-salan 4 catalyzes the diastereo-and enantioselective monoepoxidation of conjugated dienes using 30% H 2 O 2 at rt or below even in the presence of other olefins and adjacent stereocenters. Its enantiomer, ent-4, provides access to the opposite diastereomer or enantiomer. The resultant chiral allylic epoxides, and the triols derived from them, are versatile synthetic intermediates as well as substructures present in many bioactive natural products. The epoxidation is highly specific for Z-olefins. For 1-acyl(silyl)oxypenta-2,4-dienes, epoxidation of the distal olefin is generally favored in contrast to the adjacent regioselectivity characteristic of Sharpless, peracid, and other directed epoxidations of hydroxylated dienes.
Epoxides are biologically important moiety that is also used as synthetic intermediates. This rev... more Epoxides are biologically important moiety that is also used as synthetic intermediates. This review aims to present the up-to-date advancements in methyltrioxorhenium (MTO)-catalyzed epoxidation of alkenes using diverse oxidizing agents.
Two routes, one based on a Michael-initiated aldol condensation and the other on an intramolecule... more Two routes, one based on a Michael-initiated aldol condensation and the other on an intramoleculer carbonyl-ene reaction, have been found to be feasible for an entry to benzo[b]fluorenones. Reaction of 4,9-dimethoxybenz[f]indenone with nitromethane in the presence of DBU gave the corresponding Michael adduct, which afforded 2-methyl-5,10-dimethoxybenzo[b]fluorenone on reaction with methacrolein under a variety of basic conditions. Similarly, 2-methallyl-4,9-dimethoxybenz[f]indenone reacted with nitromethane to give the corresponding Michael adduct, Nef reaction of which furnished 3-formyl-2-methyl-4,9-dimethoxybenz[f]indanone. This underwent ene-cyclization under the influence of SnCl4. 5H2O, and yielded 2-methyl-5,10-dimethoxybenzo[b]fluorenone.
Abstract DBU-CH3I has been poised to be a substitute for diazomethane in the preparation of methy... more Abstract DBU-CH3I has been poised to be a substitute for diazomethane in the preparation of methyl esters from carboxylic acids. The reactions can be carried out in commercial untreated acetone and acetonitrile, which have been exemplified with several methyl ...
DBU catalyzed condensation of phthalaldehydic acids and 1,3-diketones has been developed to be a ... more DBU catalyzed condensation of phthalaldehydic acids and 1,3-diketones has been developed to be a general method for the synthesis of 3-substituted phthalides. This method, in combination with mercuric acetate mediated oxidative aromatization has been utilized for the regiospecific synthesis of isopestacin (9) and cryphonectric acid (10).
The preparation of the title compounds is accomplished with high (E)-stereoselectivity where only... more The preparation of the title compounds is accomplished with high (E)-stereoselectivity where only elemental sulfur is lost.
A new catalyst Ti(IV)-salan system efficiently promotes the diastereo- and enantioselective monoe... more A new catalyst Ti(IV)-salan system efficiently promotes the diastereo- and enantioselective monoepoxidation of conjugated dienes using H2O2 even in the presence of other olefins and adjacent stereocenters.
Enantiomerically enriched vinyl epoxides offer enticing synthetic versatility and also occur as l... more Enantiomerically enriched vinyl epoxides offer enticing synthetic versatility and also occur as labile metabolites in many biosynthetic pathways of medicinal significance. Herein, we describe an efficient, highly stereo- and regiospecific mono-epoxidation of conjugated dienols using a Ti(IV) catalyst and hydrogen peroxide at rt.
Ti(IV)-salan 4 catalyzes the diastereo-and enantioselective monoepoxidation of conjugated dienes ... more Ti(IV)-salan 4 catalyzes the diastereo-and enantioselective monoepoxidation of conjugated dienes using 30% H 2 O 2 at rt or below even in the presence of other olefins and adjacent stereocenters. Its enantiomer, ent-4, provides access to the opposite diastereomer or enantiomer. The resultant chiral allylic epoxides, and the triols derived from them, are versatile synthetic intermediates as well as substructures present in many bioactive natural products. The epoxidation is highly specific for Z-olefins. For 1-acyl(silyl)oxypenta-2,4-dienes, epoxidation of the distal olefin is generally favored in contrast to the adjacent regioselectivity characteristic of Sharpless, peracid, and other directed epoxidations of hydroxylated dienes.
Epoxides are biologically important moiety that is also used as synthetic intermediates. This rev... more Epoxides are biologically important moiety that is also used as synthetic intermediates. This review aims to present the up-to-date advancements in methyltrioxorhenium (MTO)-catalyzed epoxidation of alkenes using diverse oxidizing agents.
Two routes, one based on a Michael-initiated aldol condensation and the other on an intramolecule... more Two routes, one based on a Michael-initiated aldol condensation and the other on an intramoleculer carbonyl-ene reaction, have been found to be feasible for an entry to benzo[b]fluorenones. Reaction of 4,9-dimethoxybenz[f]indenone with nitromethane in the presence of DBU gave the corresponding Michael adduct, which afforded 2-methyl-5,10-dimethoxybenzo[b]fluorenone on reaction with methacrolein under a variety of basic conditions. Similarly, 2-methallyl-4,9-dimethoxybenz[f]indenone reacted with nitromethane to give the corresponding Michael adduct, Nef reaction of which furnished 3-formyl-2-methyl-4,9-dimethoxybenz[f]indanone. This underwent ene-cyclization under the influence of SnCl4. 5H2O, and yielded 2-methyl-5,10-dimethoxybenzo[b]fluorenone.
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