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

Abstract

A visible-light-promoted iodine-mediated homo-coupling of diazo was first described. A series of tetrasubstituted olefins were synthesized in high yields and with low to high Z-selectivities from phenyldiazoacetates. For 3-diazooxindoles, isoindigo derivatives were provided in moderate to high yields and with excellent E-selectivities. Experimental results showed that the reaction proceeded through a diiodo intermediate. The synthetic usefulness of this reaction was illustrated by the synthesis of maleimide derivatives and dispiro epoxy.

Visible Light-Induced Reactions of Diazo Compounds and Their Precursors

“…Inspired by this work, Chen and co-workers later reported a photochemical iodine-mediated method for homocoupling of diazo substrates, enabling synthesis of tetrasubstituted alkenes. 208 In 2023, Wu's group developed an iodine-mediated multicomponent coupling between trifluorodiazoethane 99.4 and aryl alkynes 99.5 (Scheme 99b). 209 This reaction involves two diazo and two alkyne components, providing a convenient access to bistrifluoromethylated conjugated trienes 99.6.…”

“…Following this, the produced iodine radical reacts with iodide, forming an anionic radical I 2 –• , which is further oxidized to regenerate iodine and the photocatalyst. Inspired by this work, Chen and co-workers later reported a photochemical iodine-mediated method for homocoupling of diazo substrates, enabling synthesis of tetrasubstituted alkenes . In 2023, Wu’s group developed an iodine-mediated multicomponent coupling between trifluorodiazoethane 99.4 and aryl alkynes 99.5 (Scheme b) .…”

DBU-Mediated Dimerization: Facile Access to 9,9′-Bifluorenylidenes and Isoindigos

“…Knowing the importance of the isoindigo core structure in conjugated polymers (CPs), organic photovoltaics (OPVs), organic field-effect transistors (OFETs) 10 and biologically important molecules, 11 we decided to explore the synthetic utility of the present methodology for the synthesis of isoindigos. On the basis of a literature search, there are a vast number of reported synthetic protocols to construct isoindigos, for example, acid-catalyzed condensation of isatins with oxindoles, 12 gold-catalyzed dimerization of 3-diazooxindoles, 13 palladium-catalyzed cyclization, 14 dimerization of oxindoles using thionyl chloride (SOCl 2 ) 15 or N-chlorosulfenylsuccinimide, 16 sodium iodide promoted dimerization of oxindoles, 17 visible-light-promoted, iodine-mediated dimerization of 3-diazooxindoles, 18 iron-catalyzed dimerization of isatins, 19 and dimerization of indoles promoted by a combination of I 2 /DMSO/K 2 S 2 O 8 . 20 Recently, we disclosed the dimerization of 3-chlorooxindoles by employing potassium ethyl xanthate for the synthesis of a range of isoindigos in yields of 52-89%.…”

Iodine-Mediated Coupling of 2,2,2-Trifluorodiazoethane and Alkynes To Access Bistrifluoromethylated 1,3,5-Trienes

“…On the basis of the experimental results and reported literature, , a proposed reaction mechanism is depicted in Scheme b. Under irradiation, 2,2-diiodo-1,1,1-trifluoroethane (CF 3 CHI 2 ) generated from iodine and CF 3 CHN 2 produced 2,2,2-trifluoro-1-iodo-ethyl radical species I .…”