Hydrochloric Acid → cis 5,6-dihydro-6-(2-ethoxycarbonylethyl)-4-(4-methoxybenzylamino)-4H-thieno[2,3-b]thiopyran

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Reaction Steps

To a solution of 2 (10.4 g, 0.039 mol) in THF (110 ml) and toluene (110 ml) at 0° is added 4-methoxybenzylamine (25.5 ml, 26.8 g, 0.195 mol). Titanium tetrachloride (2.2 ml, 3.8 g, 0.02 mol) is added to the cold solution and the resulting mixture is stirred for 0.75-1 hour. The mixture is added to a cold (0°) stirred suspension of NaBH4 (4.5 g, 0.12 mol) in EtOH (900 ml). The resulting mixture is stirred for about 1 hour and acidified to pH 1 with 3N HCl. The solvent is removed in vacuo and the residue partitioned between EtOAc and saturated NaHCO3 solution. The EtOAc layer is separated, dried and concentrated to dryness to yield 3 wherein R1, R2, R3 and R4 are each H.

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