Cyclohexanone → Cyclohexanone, 2-(hydroxymethylene)-

Beteiligte Stoffe

Reaktionsschritte

As in the previous example, 200 g (2.0 mol) of cyclohexanone was reacted with ethyl formate to give 140 g of 2-hydroxymethylenecyclohexanone, XXVIIb, bp 71°-74° C (0.6 mm). Forty grams (0.32 mol) of this substance was dissolved in 150 ml CH2Cl2. containing 30 g of pyridine and treated at -5° C with a solution of 64 g (0.34 mol) of p-toluenesulfonyl chloride and 16 g of pyridine in 150 ml CH2Cl2. The reaction was stirred overnight at this temperature. Work-up in the usual manner gave the enol tosylate XXVIIIb. This was not isolated but added directly to a solution of 150 g (1.0 mol) NaI in dry acetone. After stirring overnight at room temperature this was worked up in the usual manner to give (E)-2-iodomethylenecyclohexanone, XXIXb, as a red oil. Again this was not isolated but was reduced with NaBH4 in EtOH to give crystalline dl-(E)-2-iodomethylenecyclohexanol, XXXb. Recrystallization from petroleum ether gave 40 g of white needles, mp 80° C.

Herkunft & Nachweise