Kentoku Gotanda

Additions of malononitrile radicals to alkenes under mild conditions using 2,2′-azobis-(2,4-dimethyl-4-methoxyvaleronitrile) (V-70) as an initiator

Abstract The attributes of 2,2′-azobis-(2,4-dimethyl-4-methoxyvaleronitrile) (V-70), which is an effective radical initiator at low temperature, in contrast to 2,2′-azobisisobutyronitrile (AIBN) are described.

Studies on tandem transesterification and intramolecular cycloaddition of nitrones. 2. Sequential bicyclization of α,α-dialkoxycarbonylnitrones with allyl alcohols

Abstract Treatment of α-methoxycarbonylnitrones with 5 equiv. of allyl alcohols in the presence of 1 equiv. of titanium tetraisopropoxide causes tandem transesterification, E , Z -isomerization of the nitrone moieties, and intramolecular cycloaddition to afford bicyclized compounds in one step. To reduce amounts of allyl alcohol, combined use of a catalytic amount of titanium tetraisopropoxide and molecular sieves 4A was found to be a more improved catalytic system. It was also found that reactions of ( Z )-allyl alcohols with α-methoxycarbonylnitrone are more facile than those of ( E )-allyl alcohols. This aspect was extended to geometry differentiated cycloaddition.

Intermolecular 1,3-dipolar cycloaddition of chiral and geometry fixed α-alkoxycarbonylnitrone, 5,6-dihydro-5-phenyl-2H-1,4-oxazin-2-one N-oxide

The 1,3-dipolar cycloaddition of (R)-5,6-dihydro-5-phenyl-2H-1,4-oxazin-2-one N-oxide[(5R)-2], a chiral and geometry fixed α-alkoxycarbonylnitrone, with alkenes 3–6 proceeded smoothly to afford cycloadducts 7–10 as main products viaβ-exo mode.

Highly asymmetric Pummerer-type reaction induced by ethoxy vinyl esters

Abstract Ethoxy vinyl esters (EVE: 2 ) were efficient reagents for promoting the asymmetric Pummerer reaction with high enantioselectivity and high yield in contrast to the generally used acid anhydrides. Increasing the electron-donating ability on the R function in EVE 2 tended to increase enantioselectivity. Consequently, effective asymmetric rearrangements were achieved using EVEs 2b,c bearing a methoxybenzoyloxy function.

A highly stereoselective synthesis of α-linked C-glycopyranosides using 2,2′-azobis-(2,4-dimethyl-4-methoxyvaleronitrile) (V-70)

Abstract α-Linked C-glycopyranosides were obtained effectively by the radical addition reaction using V-70, an effective radical initiator under mild conditions.

Efficient stereoselective synthesis of α-C-glycopyranosides using 2,2′-azobis(2,4-dimethyl-4-methoxyvaleronitrile) [V-70]

Abstract Efficient synthesis of α - C -glycopyranosides through a radical addition reaction using 2,2′-azobis(2,4-dimethyl-4-methoxyvaleronitrile) [V-70] as an initiator under mild condition was developed. This method made it possible to completely control the stereocenter at the anomeric position and obtain only the α-anomer in high yield compared with AIBN, Et 3 B, and photo irradiation methods.

A novel efficient sulfenylation method using quinonemono-O,S-acetals under mild conditions

A novel method for sulfenylation induced by aromatization of quinone mono-O,S-acetals is described.