Propargylic trichloroethyl ethers

Fig. 36 Chromium(II)-catalyzed cyclizations of propargylic 2,2,2-trichloroethyl ethers to 3-substituted furans...

A variety of 3-substituted furans, including the natural perillene and dendrolasin, are obtained in good yields via reductive annulation of 2,2,2-trichloroethyl propargyl ethers... 

A solution of 2,2,2-trichloroethyl propargyl ether (1 mmol) in THF (2 ml) was added to a stirred, room-temperature suspension of dry CrCl3 (15 mol%), Mn powder (4 mmol), and freshly distilled TMSC1 (4 mmol) in THF (8 ml) under an argon atmosphere. After the addition, the reaction mixture was heated at 60 °C. After 12 h, the reaction mixture was cooled and quenched with water, and extracted three times with ether. After removal of the solvent, the residue was chromatographed on silica gel to give a product in 85% yield [97]. 

Reductive annulation of 1,1,1-trichloroethyl propargyl ethers using a catalytic amount of Cr(II) generated by Mn-Me3SiCl provided 3-substituted furans in high yields. Some natural products, such as perillene and dendrolasin, were prepared utilizing this procedure <02OL1387>. 

Reductive cyclization of trichloroethyl propargyl ethers using manganese and catalytic amounts of CrCl2 in the presence of TMSCl provided 3-substituted furans in high yields (Equation 27). The feasibility of this reaction has been demonstrated in the synthesis of the natural products perillene and dendrolasine <20020L1387>. 

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