摘要:
The reaction of triethyl 3-methyl-4-phosphonobut-2-enoate (1) with three alkyl halides AlkX (Alk = Pr-i, Me2CHCH2CH2, and c-C5H9; X = Br, I) in the system KOH(solid)-DMF-(Bu4NBr)-N-n at similar to 20 degrees C gives exclusively products of alkylation at C(2) with Delta(2) and/or Delta(3) position of the double bond. Under the same conditions, the reaction of 1 with MeI gives a mixture of products with different substitution pat erns. Only the use of an ion pair extraction technique affords 2-methyl-Delta(2)-products selectively, albeit in rather moderate yields. The Horner-Emmons olefination of PhCHO with the resulting phosphonates gives ethyl 2-alkyl-3-methyl-5-phenylpenta-2,4-dienoates in high yields.