Reaction #10704

Reaction equation

3,4-dimethoxythiophene

(S)-1,2-propanediol

ethyl acetate

→

product

Yield 69.5%

2-methyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine

Yield 69.5%

Solvents

toluene

Conditions

Workup

1. 1
   Washwashed with NaHCO3
2. 2
   Concentrationthe organic phase was concentrated
3. 3
   FiltrationSubsequent filtration over SiO2

Procedure

A solution of 3,4-dimethoxythiophene (5.18 g), (S)-1,2-propanediol (3.0 g) and p-toluenesulfonic acid monohydrate (100 mg) in toluene (50 ml) was heated at 95° C. during which a continuous stream of nitrogen was passed over the solution. After 30 h the reaction mixture was poured into ethyl acetate, washed with NaHCO3 and the organic phase was concentrated. Subsequent filtration over SiO2 using n-hexane as eluant resulted in pure product (3.90 g). GC-MS: 156 (purity>99%); 1H-NMR (CDCl3): δ 6.30 (2×d, 2H), 4.26 (m, 1H), 4.15 (dd, 1H), 3.82 (dd, 1H), 1.35 (d, 3H) ppm; specific rotation [α]=−46° at 25° C. and 436 nm in hexane (c=0.066).

Source