Reaction of Lithiated Bis methylthio methane with Carbon Dioxide

8 Reaction of Lithiated Bis(methylthio)methane with Carbon Dioxide 

1-1 four-necked, round-bottomed flask equipped with a long gas-inlet tube, a thermometer and an efficient mechanical stirrer. The fourth neck is left open. 

2-Substituted 1,3-dithianes have been carboxylated with good yields. The usual procedure involves pouring the solution of the lithiated dithiane onto powdered dry ice, covered with Et20 (the addition may also be carried out by means of a syringe) [1,2]. With the unsubstituted dithiane the yields were moderate, due to occurrence of a very fast trans-metallation [2]. 

Dry THF (150 ml) is placed in the flask. Carbon dioxide is introduced from a cylinder, while the THF is vigorously stirred and the flask is cooled in a bath with liquid nitrogen. When the temperature has dropped to below — 80 °C, the flow of carbon dioxide is increased to about 3 1/min (a flow-meter should be used). The temperature of the solution is kept closely around — 90 °C. When after 3 min, a large amount of C02 has dissolved, the addition of the solution (0.10 mol) of the lithiated 

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