Synthesis of Substituted Pyridines via Regiocontrolled [4 + 2] Cycloadditions of Oximinosulfonates
摘要:
Diels-Alder cycloadditions of oximinosulfonate 8 with a variety of 1,3-dienes proceed with regiochemistry opposite to that observed with conventional imino dienophiles, providing expeditious synthetic routes to substituted pyridines, tetrahydropyridines, and pyrrolines. The oximinosulfonate 8 is prepared in one convenient synthetic operation from Meldrum's acid and reacts with conjugated dienes at -78 degrees C in the presence of 2 equiv of dimethylaluminum chloride to afford [4 + 2] cycloadducts in good to excellent yield. Exposure of these cycloadducts to the action of NaOMe and N-chlorosuccinimide in methanol-THF at room temperature then produces substituted pyridines. The utility of this new two-step annulation protocol is demonstrated in total syntheses of the pyridine alkaloids fusaric acid and (S)-(+)-fusarinolic acid. Heating the [4 + 2] cycloadducts derived from 8 in a mixture of acetonitrile and pH 7 phosphate buffer induces an unusual Stieglitz-type rearrangement leading to the formation of interesting spirobicyclic pyrrolines.
Cyanocarbonylation of Amines with 5-Tosyloxyimino-2,2-dimethyl-1,3-dioxane-4,6-dione
摘要:
5-Tosyloxyimino-2,2-dimethyl-1,3-dioxane-4,6-dione (3), prepared by the reaction of 5-hydroxyimino-2,2-dimethyl-1,3-dioxane-4,6-dione sodium salt (2) with tosyl chloride, was treated with various amines (4a-c and 6a,b) in the presence of triethylamine to give the corresponding N-cyanocarbonyl derivatives (5a-c and 7a,b). However, reaction of 3 with benzyl alcohol gave rise to the formation of dibenzyl carbonate (10).
An efficient and interesting N-centered umpolung method has been disclosed to construct beneficial S–N bonds, furnishing N-sulfenylimines, which can readily be converted into the corresponding sulfonamide derivatives in a one-pot sequential operation. N-Sulfenylimines are potent intermediates in organic synthesis, whereas sulfonamides are of major molecular interest due to their rich biological activities
All possible isomers of N-beta-D-glucopyranosyl aryl-substituted oxadiazolecarboxamides were synthesised. O-Peracetylated N-cyanocarbonyl-beta-D-glucopyranosylamine was transformed into the corresponding N-glucosyl tetrazole-5-carboxamide, which upon acylation gave N-glucosyl 5-ary1-1,3,4-oxadiazole-2-carboxamides. The nitrite group of the N-cyanocarbonyl derivative was converted to amidoxime which was ring closed by acylation to N-glucosyl 5-aryl-1,2,4-oxadiazole-3-carboxamides. A one-pot reaction of protected beta-D-glucopyranosylamine with oxalyl chloride and then with arenecarboxamidoximes furnished N-glucosyl 3-aryl-1,2,4-oxadiazole-5-carboxamides. Removal of the O-acetyl protecting groups by the Zemplen Method produced test compounds which were evaluated as inhibitors of glycogen phosphorylase. Best inhibitors of these series were N-(beta-D-glucopyranosyl) 5-(naphth-1-yl)-1,2,4-oxadiazol-3-carboxamide (K-i = 30 mu M), N-(beta-D-glucopyranosyl) 5-(naphth-2-y1)-1,3,4-oxadiazol-2-carboxamide (K-i= 33 mu M), and N-(beta-D-glucopyranosyl) 3-phenyl-1,2,4-oxadiazol-5-carboxamide (K-i= 104 mu M). ADMET property predictions revealed these compounds to have promising oral drug-like properties without any toxicity. (C) 2013 Elsevier Ltd. All rights reserved.
PREPARATION OF SUBSTITUTED PYRIDINES VIA REGIOCONTROLLED [4 + 2] CYCLOADDITIONS OF OXIMINOSULFONATES: METHYL 5-METHYLPYRIDINE-2-CARBOXYLATE
作者:Danheiser, Rick L.、Renslo, Adam R.、Amos, David T.、Wright, Graham T.、Krause, Helga、Fürstner, Alois
DOI:10.15227/orgsyn.080.0133
日期:——
Synthesis of Substituted Pyridines via Regiocontrolled [4 + 2] Cycloadditions of Oximinosulfonates
作者:Adam R. Renslo、Rick L. Danheiser
DOI:10.1021/jo981014e
日期:1998.10.1
Diels-Alder cycloadditions of oximinosulfonate 8 with a variety of 1,3-dienes proceed with regiochemistry opposite to that observed with conventional imino dienophiles, providing expeditious synthetic routes to substituted pyridines, tetrahydropyridines, and pyrrolines. The oximinosulfonate 8 is prepared in one convenient synthetic operation from Meldrum's acid and reacts with conjugated dienes at -78 degrees C in the presence of 2 equiv of dimethylaluminum chloride to afford [4 + 2] cycloadducts in good to excellent yield. Exposure of these cycloadducts to the action of NaOMe and N-chlorosuccinimide in methanol-THF at room temperature then produces substituted pyridines. The utility of this new two-step annulation protocol is demonstrated in total syntheses of the pyridine alkaloids fusaric acid and (S)-(+)-fusarinolic acid. Heating the [4 + 2] cycloadducts derived from 8 in a mixture of acetonitrile and pH 7 phosphate buffer induces an unusual Stieglitz-type rearrangement leading to the formation of interesting spirobicyclic pyrrolines.
Cyanocarbonylation of Amines with 5-Tosyloxyimino-2,2-dimethyl-1,3-dioxane-4,6-dione
5-Tosyloxyimino-2,2-dimethyl-1,3-dioxane-4,6-dione (3), prepared by the reaction of 5-hydroxyimino-2,2-dimethyl-1,3-dioxane-4,6-dione sodium salt (2) with tosyl chloride, was treated with various amines (4a-c and 6a,b) in the presence of triethylamine to give the corresponding N-cyanocarbonyl derivatives (5a-c and 7a,b). However, reaction of 3 with benzyl alcohol gave rise to the formation of dibenzyl carbonate (10).