Iodine transfer cyclization mediated by DIBAL-H/THF

Abstract

The combination of DIBAL-H/THF in a 1∶1 ratio offers a unique and useful protocol for iodine transfer cyclization via a radical pathway; different iodo acetals are employed to obtain the corresonding tetrahydrofuran derivatives in good to excellent yield.

References

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17. Experimental procedure for 4(it is important to follow the order of addition of substrates for these experiments): Into a dry, argon-flushed flask kept under a static pressure of argon is placed a 1.0 molar solution of DIBAL-H (1.76 ml, 1.76 mmol) in hexane. To the cooled solution (0 °C) is added sequentially THF (127 mg, 1.76 mmol) and the iodide (467 mg, 1.76 mmol) in hexane (1 ml). The solution is stirred at 0 °C for 15 min and then allowed to attain room temperature and stirred overnight. The reaction mixture was then quenched with 1 M HCl, extracted with Et₂O and washed several times with water, dried (MgSO₄) and then the solvent was evaporated to provide the crude product. After purification by chromatography on silica gel (10% EtOAc in hexanes), 421 mg (90%) of the title compound was obtained.
18. All our attempts to form the six-membered ring as well as to promote the isomerization across a double bond failed.