Cobalt-Catalyzed Oxygenation/Dearomatization of Furans

Abstract

The dearomatization of aromatic compounds using cobalt(II) acetylacetonate with triplet oxygen and triethylsilane converts furans, benzofurans, pyrroles, and thiophenes to a variety of products, including lactones, silyl peroxides, and ketones.

Cobalt‐Catalyzed Hydrogen‐Atom Transfer Induces Bicyclizations that Tolerate Electron‐Rich and Electron‐Deficient Intermediate Alkenes

“…Product 8 c , a known compound, was formed along with products of terminal to internal alkene isomerization of the substrate; owing to the formation of multiple products of similar polarity, it could only be obtained in about 90 % purity. The product of furan termination ( 8 e ) was not observed, which was unexpected; however, Co‐catalyzed MHAT to furans is known . The failure to produce 8 f and 8 g by termination with electron‐poor arenes mirrors our results with similar acrylonitrile substrates shown in Figure .…”

Cobalt‐Catalyzed Hydrogen‐Atom Transfer Induces Bicyclizations that Tolerate Electron‐Rich and Electron‐Deficient Intermediate Alkenes

“…In light of Shigehisasr eport on hydroarylation of unactivated alkenes, [11d] we changed the substrate to include the trisubstituted, methyl-bearing internal alkene that is more typical of bioinspired polyene cyclizations.S everal of these substrates reacted productively,generating the tricyclic compounds 8a-d with reasonable efficiency [23] under nearly identical reaction conditions used for the nitrile substrates ( Figure 3);i nt hese cases the less sterically crowded catalyst C2 proved slightly superior to C1.P roduct 8c,aknown compound, [24] was formed along with products of terminal to internal alkene isomerization of the substrate;o wing to the formation of multiple products of similar polarity,i tc ould only be obtained in about 90 %p urity.T he product of furan termination (8e)w as not observed, which was unexpected; however, Co-catalyzed MHATt of urans is known. [25] The failure to produce 8f and 8g by termination with electronpoor arenes mirrors our results with similar acrylonitrile substrates shown in Figure 2.…”

Hydroperoxidations of Alkenes using Cobalt Picolinate Catalysts

“…Both α,β-unsaturated ketones and esters were effective substrates, although the latter alkenes, which should be less electron-deficient than enones, required longer reaction times. Addition of t -BuOOH shortened the induction period of the reactions, , but no compounds containing OO t- Bu groups were isolated from the reaction mixture. , Addition of chloroform in some, but not all, cases increased yields between 5 and 10%.…”