Abstract: The iodine-catalyzed Prins cyclization of homoallylic alcohols and aldehydes was investigated under metal-free conditions and without additives. Anhydrous conditions and inert atmosphere are not required. The reaction of 2-(3,4-dihydronaphthalen-1-yl)propan-1-ol and 21 aldehydes (aliphatic and aromatic) in CH2Cl2 in the presence of 5 mol % of iodine gave 1,4,5,6-tetrahydro-2H-benzo[f]isochromenes in 54%–86% yield. Under similar conditions, the Prins cyclization of six alcohols containing an endocyclic double bond (primary, secondary, or tertiary) led to dihydropyrans in 52%–91% yield. The acyclic homoallylic alcohols gave 4-iodo-tetrahydropyran in 29%–41% yield in the presence of 50 mol % of iodine. This type of substrate is the main limitation of the methodology. The relative configuration of the products was assigned by NMR and X-ray analysis. The mechanism and the ratio of the products are discussed, based on DFT calculations.
Keywords: isochromene; pyrans; prins cyclization; iodine; DFT calculations
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Reddy, K.R.K.K.; Rosa, I.M.L.; Doriguetto, A.C.; Bastos, E.L.; Silva, L.F., Jr. Iodine-Catalyzed Prins Cyclization of Homoallylic Alcohols and Aldehydes. Molecules 2013, 18, 11100-11130.
Reddy KRKK, Rosa IML, Doriguetto AC, Bastos EL, Silva LF, Jr. Iodine-Catalyzed Prins Cyclization of Homoallylic Alcohols and Aldehydes. Molecules. 2013; 18(9):11100-11130.
Reddy, Kachi R.K.K.; Rosa, Iara M.L.; Doriguetto, Antônio C.; Bastos, Erick L.; Silva, Luiz F., Jr. 2013. "Iodine-Catalyzed Prins Cyclization of Homoallylic Alcohols and Aldehydes." Molecules 18, no. 9: 11100-11130.