Dichloromethane → Ethyl-4-[[(1,1-dimethylethoxy)carbonyl]amino]-4,5-dihydro-2-thiophenecarboxylate

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Reaction Steps

Into an ice cooled stirring solution containing the crude alcohol obtained in Step C, 75 ml of CH2Cl2, and 10.5 ml (74 mmole) of Et3N was added 2.9 ml (37 mmole) of mesyl chloride while maintaining the system under a positive argon atmosphere. The reaction was stirred an additional 5 minutes at 0° C. and then 3 hours at 25° C. The reaction was poured into a separatory funnel containing 200 ml Et2O and successively washed with 70 ml water, 1N HCl until the aqueous wash tested acidic; 15 ml water and 50 ml brine, and dried over MgSO4. Removal of the solvent at reduced pressure afforded 6.5 g of a brown oil which was purified by flash chromatography (eluting with 15% and then 20% EtOAc/Hexanes) to yield 3.97 g of product. This material exhibited the following optical rotation [α]Damb =+122.8° at a concentration of 0.5M in ethanol. The highest rotation observed for the R enantiomer under similar conditions was -128.1°.

Provenance & Evidence