Green chemistry: solvent- and metal-free Prins cyclization. Application to sequential reactions

Abstract

Prins cyclization between a homoallylic alcohol and an aldehyde, promoted by trimethylsilyl halide, afforded 4-halo-tetrahydropyrans with good to excellent yields. Thanks to the absence of the solvent and metal, the THP thus obtained have been implicated without purification in several other reactions, in a sequential way, affording in particular new indole derivatives.

Sequential Oxidation-Prins Reaction Processes Induced by the Same Iron Salt: Direct Access to 2-Aryl-4-Chloro-Tetrahydropyrans from Benzyl ­Alcohols

“…However, this process was successful only under neat conditions. 18 While the present process was carried out at 0.5 M concentration, a plausible synergistic effect between iron salts and TMSCl was suspected. The importance of the presence of iron salts was clearly demonstrated by placing benzaldehyde and 3, only in the presence of trimethylsilyl chloride in dichloromethane.…”

Nickel-Catalyzed Diastereoselective Alkyl–Alkyl Kumada Coupling Reactions

“…After the addition, the solution was still stirred for 30 min at -20°C. It was then quenched by the addition of 5 mL of a saturated solution of NH 4 Cl and 5 mL of water. The organic phase in the resulting solution mixture was extracted with ether (3 times, 10 mL each), dried over Na 2 SO 4 , filtered, and subject to GC analysis.…”

“…The solution was then slowly added by the syringe pump over 2 h to a solution containing [( Me N 2 N)Ni-Cl] (15 mg, 0.043 mmol), 1 mL of THF, TMDEA (25 µL, 0.17 mmol), and the iodide or bromide (0.5 mmol) at -20 o C. After the addition, the solution was still stirred for 30 min at r.t. It was then quenched by the addition of 5 mL of a saturated solution of NH 4 Cl and 5 mL of water. The organic phase in the resulting solution mixture was extracted with ether (3 times, 10 mL each), dried over Na 2 SO 4 , filtered, and subject to GC analysis.…”

Gallium(III) Iodide Mediated Mild and Efficient Method for Synthesis of 4-Iodotetrahydropyrans by Cross-Cyclization of Epoxides and Homoallylic Alcohols

“…Zurwerra et al [5] reported the synthesis of (-)-dactylolide from 4-iodotetrahydropyran derivative. Even though there is considerable demand for 4-iodotetrahydropyrans, limited methods are available in the literature [6][7][8][9][10][11]. Among the existing methods, Prins cyclization is the common and widely used method for the tetrahydropyrans synthesis.…”