Tandem Radical Cyclization Research Articles

A highly diastereoselective synthesis of cis-4a-aryloctahydrocyclopenta(c)pyridine derivatives through tandem radical cyclization of .ALPHA.-amino radical-polyene species.

8a-Aryloxazolo[3, 4-a]cyclopenta[d]pyridines (9a-c) were prepared via a route involving radical cyclization of α-acylamino radical-polyene species generated by treatment of 4-phenylthiooxazolidin-2-ones (8a-c) with tri-n-butyltin hydride in the presence of azobisisobutyronitrile (AIBN). Conversion of 9a to cis-octahydro-2, 5-dimethyl-4a-phenylcyclopenta[c]pyridine (19) was successfully achieved via a route involving ring cleavage of the oxazolidinone ring of 9a, oxidation of hydroxymethyl group, and decarbonylation.

The Tandem Radical Cyclization Approach to Angular Triquinanes : Model Studies and the Total Synthesis of (±)-Silphiperfolene and (±)-9-Episilphiperfolene

Models studies and the total synthesis ofsilphiperfol-6-ene ( 4, seven steps) and 9-episilphiperfol-6-ene ( 14, five steps) are reported. The use of a tandem radical cyclization permits rapid construction of the requisite tricyclic nucleus. In the most direct approach, the key tandem cyclization ( 18 → 19) produces the C-9 epimer as the major product. In a modified approach, cyclization of the dioxolane ketal derived from 18 ( 27 → 28) produces a useful excess of the natural isomer. Interesting observations on the rapid prototropic isomerization of a vinyl silane to an allyl silane ( 21→ 22+23) are also discussed.

ChemInform Abstract: Tandem Radical Cyclization Approach to Angular Triquinanes. A Short Synthesis of (±)‐Silphiperfol‐6‐ene (VIII) and (±)‐9‐Episilphiperfol‐6‐ene (IX).

ChemInform Abstract: Tandem Radical Cyclization Approach to Angular Triquinanes. A Short Synthesis of (±)‐Silphiperfol‐6‐ene (VIII) and (±)‐9‐Episilphiperfol‐6‐ene (IX).

Effect of a-strain on a synthesis of cis-fused 4a-aryloctahydro-1H-cyclopenta[c]pyridine derivatives through tandem radical cyclisation of an α-acylamino–polyene system

An efficient synthesis of the cis-fused 4a-aryloctahydro-1H-cyclopenta[c]pyridine ring sustem, an analogue of 4a-aryidecahydroisoquinoline, was achieved through a teandem redical approach by cyclisation of free radical–polyene species.

Radical-initiated polyolefinic cyclizations in condensed cyclopentanoid synthesis. Total synthesis of (±)-Δ 9(12)-capnellene

Total synthesis of Δ 9(12)-capnellene is reported. The key reaction involves construction of two rings in a single step via a tandem radical cyclization.

Radical-initiated polyolefinic cyclizations in linear triquinane synthesis. model studies and total synthesis of (±)-hirsutene

Details of a novel radical-initiated polyolefinic cyclization approach to linear condensed cyclopentanoids are reported. The strategy is executed in three stages: (1) Sn2′-anti opening of a vinyl lactone to produce a trans-3,5-disubstituted cyclopentene, (2) rapid elaboration to a cyclization precursor, and (3) single step tandem radical cyclization to produce a cis-anticis tricyclo[3.3.0]undecane. Model substrates 16a and 16b give high yields of tricyclic products 17 and 18 , respectively. An effort to rationalize the interesting endo selectivity via the Beckwith transition state model is proposed. Cyclizations of 28 and 29 to 30 and 31 demonstrate the viability of a tandem hexenyl-hexynyl cyclization. The work culminates with a total synthesis of (±)hirsutene. A selective approach to methyl substituted vinyl lactones by Claisen rearrangement-phenylselenolactonization-elimination of acetoxy cyclopentenols is exemplified by the synthesis of 12 . Tandem cyclization of 38 produces hirsutene ( 1 ) in a single step. Alternatively, cyclization of 37 yields trimethylsilyl hirsutene.