5365-37-7Relevant academic research and scientific papers
Cascade radical mediated macrocyclisation-transannulation reactions leading to ring-fused bicycles
Pattenden, Gerald,Smithies, Allison J.,Tapolczay, David,Walter, Daryl S.
, p. 7 - 20 (2007/10/03)
The scope for tandem radical mediated macrocyclisation-transannulation processes in the elaboration of ring-fused carbocycles has been examined.Thus, a range of E-iodo dienones viz. 21, 30b, 40, 42 and 44 were first prepared using synthetic sequences based on sound literature precedent.Treatment of the iodo dienone 21 with Bu3SnH-AIBN led to a 3:2 mixture of trans- and cis-isomers of 1-decalone, 35 and 36, respectively, in a combined yield of 72percent, whereas the positional isomer 30b of 21 underwent 10-endo macrocyclisation and transannulation to a 1:1 mixture of trans-1-decalone 35 and cis-octahydroazulen-1-one 39 (combined yield 68percent), resulting from competitive 6-exo/5-exo transannular cyclisation from the intermediate cyclodecenone radical 38.In further investigations of the scope for sequential radical macrocyclisation-transannulations in the synthesis of bicyclic systems, the iodo dienone 40 was found to undergo regioselective cyclisation to the cis-tetralone 41 (50percent), whereas the iodo dienone 42 produced only (Z)-cyclooct-3-enone 54 and none of the expected bicyclooctanone 43 on treatment with Bu3SnH-AIBN.Only the 4-cyclopentylcyclohexanone 61, and none of the hoped for 7,6-bicyclic ketone 45, was produced from radical cyclisation of the iodo dienone 44.The differing reaction pathways followed by the iodo dienones 21, 30b, 40 and 42 have been rationalised in terms of the conformational preferences of the macrocyclic α-keto radical intermediates, e.g. 32, 38 and 52 involved in the various cyclisations supported by some preliminary MM2 studies and calculations.
Sequential Radical Macrocyclisation-Transannulation Approach to Ring-fused Bicycles
Pattenden, Gerald,Smithies, Allison J.,Walter, Daryl S.
, p. 2413 - 2416 (2007/10/02)
The scope for tandem radical mediated macrocyclisation-transannulation processes (Scheme 1) in the elaboration of polycycles is illustrated with the facile syntheses of linear 5,6-, 6,6- and 5,7-ring fused carbobicycles, viz 7,8,11,13 from appropriate iododienone precursors, viz 1,2,12, on treatment with Bu3SnH-AIBN
Free-Radical Ring Expansion of Fused Cyclobutanones: Stereospecific Construction of 5,7-, 6,7-, 7,7-, 8,7-, and 5,8-Cis-Fused Bicyclic Systems
Dowd, Paul,Zhang, Wei
, p. 7163 - 7171 (2007/10/02)
A new method of appending seven- and eight-membered rings to cycloalkenes is described.Treatment of selected alkene precursors with an ω-bromoalkyl ketene or a keteniminium salt leads to haloalkyl cyclobutanone formation.Tri-n-butyltin hydride promoted ring expansion then yields the annulated product.Since the initial cyclobutanone is cis fused, the final product is also produced stereospecifically with a cis ring fusion.
