Manganese(III) Acetate Mediated Oxidative Radical Cyclizations. Toward Vicinal All-Carbon Quaternary Stereocenters

Abstract

Manganese(III) acetate mediated oxidative radical cyclizations have been used to synthesize a range of densely functionalized and sterically congested cyclopentane-lactones. A number of the resulting lactones contain vicinal all-carbon quaternary stereocenters adjacent to a tertiary benzylic stereocenter and are formed with high levels of stereocontrol.

Titanocene(III) chloride mediated radical induced addition-elimination route to the synthesis of racemic and optically active trisubstituted tetrahydrofurans: Formal synthesis of magnofargesin and 7′-epimagnofargesin

“…Most of the compounds described are already reported in the literature and are characterized by NMR, IR and MASS spectral studies and have been compared with authentic samples. Allylic alcohols 4a-g 13 and the epoxides 5a-g 14c, [15][16][17] were prepared following the standard literature procedures.…”

A Short Synthesis of Aphanamol I in Both Racemic and Enantiopure Forms

“…Application of this retrosynthetic transformation leads to the [3.3.0]‐bicyclic enol ether 2 , which would be readily prepared from the corresponding [3.3.0]‐bicyclic lactone 3 following methylenation (Figure ) . We have recently used oxidative radical methodology for the synthesis of [3.3.0]‐bicyclic lactones by the cyclization of 4‐pentenyl malonates . Application of such an oxidative radical cyclization to an appropriately functionalized 4,6‐heptadienyl malonate 4 should yield the corresponding alkenyl‐substituted [3.3.0]‐bicyclic lactone 3 .…”

“…[12] We have recently used oxidative radicalm ethodology for the synthesis of [3.3.0]-bicyclic lactones by the cyclization of 4-pentenyl malonates. [14,[15][16][17][18][19] Application of such an oxidative radicalc yclization to an appropriately functionalized 4,6-heptadienyl malonate 4 should yield the corresponding alkenyl-substituted [3.3.0]-bicyclic lactone 3.B ased on the Beckwith-Houkm odel [20,21] for 5-exo-trig radicalcyclizations and our own previous experience, we would predict that the oxidative radicalc yclization would proceed through the pre-transition state assembly 5 with the iso-propyl group residingi n a pseudo-equatorial position of the chair-like transition state with minimization of allylic strain. Preparation of the dienyl malonate such as 4 in enantioenriched form was to be achieved using the beautiful catalytic enantioselective conjugate addition methodologyr ecently reported by Nishimura and Hayashi, [22,23] with the requisite diene being formed by ahydroboration-Suzuki cross-coupling sequence.…”

Recent advances in manganese(iii) acetate mediated organic synthesis

“…65 The mutual influence of Mn(OAc) 3 and Cu(OTf) 2 in the cyclization of 1,2-disubstituted alkene malonates 121a-j followed by that on sterically more challenging trisubstituted 123a-f and fully substituted alkene substrates 126 to yield the corresponding [3.3.0]bicyclic c-lactones, was observed in the study. 66 Treatment of 1,2disubstituted alkene malonates 121a-121j with 2 equiv. of Mn(OAc) 3 and 1 equiv.…”