CID 406 → 3-Methyl-5-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4-pentadienylphosphonic Acid, Diethyl Ester

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Reaction Steps

A mixture of the vinyl phosphonate produced in accordance with Example VIII (943 mg, 2.77 mmoles) and 99 mg (0.88 mmoles) of potassium tert-butoxide in 12 mL of anhydrous dimethyl sulfoxide (DMSO) was stirred, protected from atmospheric moisture, at 20° C. for 80 minutes. The product was isolated by dilution of the reaction mixture with 100 mL of ether and subsequent washing with 120 mL portions of 10% aqueous sodium chloride (4×120 mL). The organic layer was then dried over anhydrous magnesium sulfate and filtered. Removal of the ether by evaporation at reduced pressure afforded 718 mg (76% yield) of the desired allylic phosphonate, whose structural integrity was confirmed by NMR analysis [δ 2.75, doublet of doublets, J=8 Hz and 22 Hz, CH2P]. In a similar manner, this allylic phosphonate could be prepared by isomerization of 3-methyl-5-(2,6,6-trimethyl-1-cyclohexen-1-yl)-1,3-pentadienylphosphonic acid, diethyl ester, produced in accordance with Example VI.

Provenance & Evidence