Efficient construction of 8-membered ring framework of vinigrol through SmI2-induced coupling cyclization

Benzannulated Cyclooctanol Derivatives by Samarium Diiodide Induced Intramolecular Carbonyl–Alkene Coupling – Scope, Limitations, Stereoselectivity

“…The mixture was stirred overnight (12-16 h), allowed to warm slowly to 10°C during this period and quenched with satd. aqueous NH 4 Cl solution. The two phases were separated and the aqueous phase was repeatedly extracted with diethyl ether.…”

“…The mixture was quenched with satd. aqueous NH 4 Cl solution, the phases were separated, and the aqueous phase was repeatedly extracted with diethyl ether. The combined organic phases were washed with water and brine and dried (Na 2 SO 4 ).…”

“…[3] Despite these obstacles, however, surprisingly efficient and flexible methods have been found. [4] One of the newer reaction modes for the construction of eight-membered rings is the cyclization of samarium ketyl compounds to olefins; [5] pioneering investigations by Molander et al [6] demonstrated with sim-dergo the samarium diiodide promoted ring-closure process. An explanation for this intriguing behaviour is presented, together with an explanation for the cis/trans selectivity.…”

“…Because of the occurrence of the bicyclo[6. 4.0]-undecane core in taxol we were interested in synthesizing this unit [7] by a samarium ketyl promoted cyclization of styrene-type precursors, which would be expected to gain additional driving force by benzylic stabilization of the intermediates involved during the 8-endo-trig reaction. We have already reported our preliminary results [8] and now wish to present full details showing the scope and limitations of the method, as well as some intriguing stereochemical features.…”

Flexible Routes to the 5‐Hydroxy Acid Fragment of the Cryptophycins

“…After stirring at 0°C for 1 h, the reaction mixture was cooled to Ϫ78°C and a solution of 3-(p-methoxybenzyloxy)propanal [17,44,45] (5, 4.8 g, 24.6 mmol) in CH 2 Cl 2 (10 mL) was added dropwise. The resulting pale yellow solution was stirred at Ϫ78°C for 1.5 h, then allowed to warm to 0°C over 30 min, and stirred at 0°C for 30 min.…”