Zn‐Mediated Reductive Addition of Isocyanides with Unactivated Tertiary Alkyl Oxalates

Abstract

A facile and efficient method is presented for the synthesis of 6‐alkylated phenanthridine, possessing hindered quaternary carbon centers, by Zn‐mediated reductive trapping of tertiary alkyl radicals with both electron‐rich and electron‐deficient aryl isocyanides using nickel as a promoter. Bench‐stable and operation‐friendly tertiary alkyl oxalates derived from abundant tertiary alkyl alcohols were first used as radical precursors for the alkylation of isocyanobiphenyl species. This reaction displays excellent functional group tolerance and broad substrate scope, allowing access to desired products in good to excellent yields.

Iron-catalyzed cross-electrophile coupling of bromostyrenes and chlorosilanes

“…Notably, (Z)-alkenyl bromide gave the trans-product 1 in 57% yield. Moderate to excellent coupling results with good chemoselectivities were also observed for β-heteroaromatic-substituted (E)-alkenyl bromides, containing various functional groups or moieties such as quinoline (19), indole (20), benzofuran (21), benzothiophene (22), thiophene (23) and pyridine (24-25). In addition, β-naphthyl-substituted (E)-alkenyl bromide ( 26) was also proved to be compatible.…”

“…As a result, the yield of 1 or 46 was hardly affected by either TEMPO or active olefins, thus precluding the engagement of the SET-initiated radical process. 22 Moreover, when the reaction was carried out under aerobic conditions, it did not work (Fig. 5, eqn ( 3)).…”

Zn-Mediated Fragmentation of N-Alkoxyphthalimides Enabling the Synthesis of gem-Difluoroalkenes

“…All of these results indicated a radical pathway might be involved in this transformation. On the basis of the observations presented above and literature reports, − a plausible reaction mechanism is proposed in Scheme b. First, a SET from Zn to NAPI 1 results in its fragmention to afford alkoxyl radical A , which further undergoes β-scission or 1,5-HAT to form the corresponding alkyl radical intermediate B .…”