2,3-ジヒドロフラン誘導体とベンズアルデヒドとの光付加反応

抄録

Paterno-Buchi reaction of benzaldehyde and 2, 3-dihydrofuran derivatives was studied. 2, 3-Dihydrofuran formed two stereoisomers of 7-phenyl-2, 6-dioxabicyclo [3. 2. 0] heptanes (Y type) selectively. Other 2, 3-dihydrofuran derivatives induced by acid catalyzed cleavage of 6-ethyl-2, 7-dioxabicyclo [3. 2. 0] hept-3-ene gave 2, 6-dioxabicyclo [3. 2. 0] heptane rings (Y type addition) and 2, 7-bicyclo [3. 2. 0] heptane rings (X type addition) in a special case. Photocycloaddition of 6-ethyl-2, 7-dioxabicyclo [3.2.0] hept-3-ene (Ib) formed two stereoisomers of 3, 6, 8-trioxatricyclo [5.2.0.0^{2, 5}] nonane skeltons (Y type) and two 4, 6, 8-trioxatricyclo-[5.2.0.0^{2, 5}] nonanes (X type). The formation of X type oxetanes was observed when an intermediate biradical was stabilized by a resonance effect. Stereoselectivity was established at the formation of X type oxetanes to form threo-aldol equivalents.