N,N,N',N'-Tetramethylethylenediamine → 4,5-difluoro-7-pentyl-2-(4-propylcyclohexyl)-8,9-dihydro-7H-furo[3,2-f]chromene

Participants

Reaction Steps

3.00 g (7.41 mmol) of 7,8-difluoro-2-pentyl-5-(4-propylcyclohexylethynyl)chroman-6-ol are initially introduced together with 0.11 ml (0.74 mmol) of TMEDA, and 4.1 ml (4.1 mmol) of diethylzinc (1 M soln. in heptane) are added to the mixture at 3° C. When the evolution of gas has subsided, 11 ml of toluene are added, and the batch is refluxed for 40 h. The solution is added to sat. ammonium chloride soln., and the mixture is extracted with toluene. The combined organic phases are washed with water and sat. sodium chloride soln. and dried using sodium sulfate. The solution is concentrated to dryness, and the residue is purified by column chromatography (SiO2, 1-chlorobutane:pentane=2:1). Further purification is carried out by repeated recrystallisation from ethanol at reduced temperature, giving 4,5-difluoro-7-pentyl-2-(4-propylcyclohexyl)-8,9-dihydro-7H-furo[3,2-f]chromene as a colourless solid having the phase sequence C 56° C. N 62° C. I (Δ∈=−6.8).

Provenance & Evidence