Visible-Light-Mediated Cyclopropanation Reactions of 3-Diazooxindoles with Arenes

Abstract

The cyclopropanation reaction of 3-diazooxindoles with arenes was first accomplished using visible-light irradiation. A series of spiro­[norcaradiene-7,3′-indolin]-2′-ones were synthesized for the first time in high yields and with excellent diastereoselectivities. The synthetic usefulness of this catalyst-free photochemical methodology is illustrated by the further controllable rearrangement and epoxidation reactions.

Stereoselective Synthesis of Tetrasubstituted Olefins via Visible-Light-Promoted Iodine-Mediated Homo-Coupling of Diazo

“…Based on these results and literature reports, , a plausible mechanism of this visible-light-promoted iodine-mediated reaction was proposed in Scheme . A quick reaction between diazo and I 2 gave the diiodo intermediate.…”

“…By comparison, the reaction of 3diazooxindole 4a in toluene and chlorobenzene gave the desired cyclopropanation product in 88 and 74% yield separately. 12 In the absence of iodobenzene, the reaction of 3-diazooxindole 4a in DCM only gave a trace amount of 5a after 24 h. Based on these observations, we speculated that the iodine element may be crucial to the homo-coupling reaction of diazo.…”

“…In the process of arene scope investigation, the reaction of 3-diazooxindole 4a in iodobenzene gave the homo-coupling product 5a in 30% yield after 24 h instead of the desired cyclopropanation product. By comparison, the reaction of 3-diazooxindole 4a in toluene and chlorobenzene gave the desired cyclopropanation product in 88 and 74% yield separately . In the absence of iodobenzene, the reaction of 3-diazooxindole 4a in DCM only gave a trace amount of 5a after 24 h. Based on these observations, we speculated that the iodine element may be crucial to the homo-coupling reaction of diazo.…”

“…We have recently developed the visible-light-promoted cyclopropanation reactions of 3-diazooxindoles 4a with arenes. 12 In the process of arene scope investigation, the reaction of 3diazooxindole 4a in iodobenzene gave the homo-coupling product 5a in 30% yield after 24 h instead of the desired cyclopropanation product. By comparison, the reaction of 3diazooxindole 4a in toluene and chlorobenzene gave the desired cyclopropanation product in 88 and 74% yield separately.…”

“…This visible-light-promoted iodine-mediated homo-coupling reaction of diazo originated from an accidental discovery. We have recently developed the visible-light-promoted cyclopropanation reactions of 3-diazooxindoles 4a with arenes . In the process of arene scope investigation, the reaction of 3-diazooxindole 4a in iodobenzene gave the homo-coupling product 5a in 30% yield after 24 h instead of the desired cyclopropanation product.…”