Synthetic studies of carbohydrate derivatives by photochemical reactions. Part 16. Synthesis of DL-apiose derivatives by photochemical cycloaddition of 1,3-dihydroxypropan-2-one derivatives with ethenediol or ethenol derivatives

Abstract

Irradiation of a benzene solution of 1,3-diacetoxypropan-2-one (5) and 1,3-dioxol-2-one (6) with a high-pressure mercury lamp gave a photocycloaddition product, (7-acetoxymethyl-3-oxo-2,4,6-trioxabicyclo[3.2.0]heptan-7-yl)-methyl acetate (7)(55% yield). Similar photocycloadditions of (5) with (Z)-vinylene diacetate (23), with (Z)-2-(benzyloxy)vinyl acetate (25), with 2,3-dihydro-1,4-dioxin (27), with vinyl acetate (28), with isopropenyl acetate (29), with ethoxyethene (30), and with 1,1-diethoxyethene (43) afforded cis-4,4-bis(acetoxymethyl)oxetan-2,3-diyl diacetate (31)(46% yield) and the trans-isomer (32)(49% yield); 2,2-bis(acetoxymethyl)-4-(benzyloxy)-oxetan-3-yl acetate (33)(composed of the two isomers; 11% and 26% yields) and 4,4-bis-(acetoxymethyl)-3-(benzyloxy)oxetan-2-yl acetate (38)(composed of the two isomers; 11% and 9% yields); (8-acetoxymethyl-2,5,7-trioxabicyclo[4.2.0]oct-8-yl)methyl acetate (34)(25% yield); 2,2-bis(acetoxymethyl)oxetan-3-yl acetate (35)(28% yield) and 4,4-bis(acetoxymethyl)oxetan-2-yl acetate (39)(15% yield); 2,2-bis(acetoxymethyl)-3-methyloxetan-3-yl acetate (36)(55% yield); (2-acetoxymethyl-3-ethoxyoxetan-2-yl)methyl acetate (37)(53% yield); and (2-acetoxymethyl-3,3-diethoxyoxetan-2-yl)methyl acetate (44)(48% yield) and ethyl 4-acetoxy-3-acetoxymethyl-3-hydroxybutyrate (45)(19% yield), respectively. The reaction of (5) with (43) was also induced thermally to give ethyl 4-acetoxy-3-(acetoxymethyl)coronate (46)(24% yield) in addition to (45)(20% yield). Photocycloaddition of diethyl mesoxalate (21) with (6) gave diethyl 3-oxo-2,4,6-trioxabicyclo[3.2.0]heptane-7,7-dicarboxylate (22)(23% yield). On the other hand, the reactions of 1,3-dimethoxy-(8) and 1,3-bis(benzyloxy)-propan-2-one (13) respectively with (6) afforded none of the expected photocycloadducts, but several products due to the intramolecular hydrogen abstraction from (8) and (13). The reaction of 2,2-dimethyl-1,3-dioxan-5-one (2) with (6) was also accompanied by predominant decomposition of (20).