Hajime Komura

Synthetic studies with carbonates. Part 6. Syntheses of 2-hydroxyethyl derivatives by reactions of ethylene carbonate with carboxylic acids or heterocycles in the presence of tetraethylammonium halides or under autocatalytic conditions

Reactions of ethylene carbonate (1a) with a variety of carboxylic acids catalysed by tetraethylammonium halides gave the corresponding 2-hydroxyethyl esters along with the diesters arising from disproportionation of the former products induced by the quaternary ammonium halides. Formation of the disproportionation products could be minimized by use of a short reaction time. The autocatalytic reactions of (1a) with strongly acidic carboxylic acids at elevated temperature gave ethylene glycol diesters selectively. Reaction mechanisms are discussed. Reactions of cyclic carbonates such as (1a) and propylene carbonate(1b) with acid anhydrides or active acyl compounds such as p-nitrophenyl acetate in the presence of tetraethylammonium iodide gave alkylene glycol diesters or 2-acyloxyalkyl aryl ethers in high yields. An attempt to extend this reaction to cyclohexane-1,2-diyl carbonate was unsuccessful, but a reaction with 1,2-epoxycyclohexane succeeded; this enabled us to examine the stereochemistry of the reaction. Finally, N-2-hydroxyethylation of a series of heterocyclic compounds having acidic imino hydrogen atoms was performed, both with tetraethylammonium iodide as catalyst and without a catalyst.

Reactions of sugar 1-carbonates with sugar derivatives bearing a hydroxy-group; novel method for preparation of orthoesters combining two monosaccharide units, and disaccharides

2,3,4,6-Tetra-O-acetyl-β-D-glucopyranose 1-carbonates (1) and (4) react with 1,2,3,4-tetra-O-acetyl-β-D-glucopyranose (2) to give 3,4,6-tri-O-acetyl-α-D-glucopyranose 1,2-(1,2,3,4-tetra-O-acetyl-6-deoxy-β-D-glucopyranos-6-anyl)orthoacetate whereas 2,3:5,6-di-O-isopropylidene-α-D-mannofuranose 1-carbonates (7) and (8) react with (2) to afford 1,2,3,4-tetra-O-acetyl-6-O-(2,3:5,6-di-O-isopropylidene-α-D-mannofuranosyl)-β-D-glucopyranose (9).

Reactions of d-mannitol carbonate derivatives catalyzed by tetraethylammonium bromide

Abstract Fusion of 1,2;3,4-di- O -isopropylidene- d -mannitol 5,6-carbonate ( 1 ) with nitrogen heterocycles in the presence of catalytic amounts of tetraethylammonium bromide ( 9 ) and with p -toluenesulfonamide present gave the corresponding 1-deoxy- d -mannitol-1-yl derivatives in good yields. Under the same reaction conditions, 1,2,3,4-tetra- O -acetyl- d -mannitol 5,6-carbonate ( 26 ) gave a good yield of 2,3,5,6-tetra- O -acetyl-1,4-anhydro- d -mannitol ( 27 ). Treatment of 1 with benzoyl chloride and 9 afforded 2- O -benzoyl-1-chloro-1-deoxy-3,4;5,6-di- O -isopropylidene- d -mannitol ( 36 ) and with acid anhydrides the 1,2-di- O -acyl derivatives of di- O -isopropylidene- d -mannitol. The use of 3,4- O -isopropylidene- d -mannitol 1,2;5,6-dicarbonate ( 37 ) with benzoyl chloride and acid anhydrides in the presence of 9 gave corresponding products through reaction of both carbonate groups. The reaction mechanisms are discussed.