New α-substituted alkylbenzene- and dialkylbenzene-1,2-diphosphonates: side-chain metalation of tetraethyl 4-methyl- and 4,5-dimethylbenzene-1,2-diphosphonates
作者:Sergey N. Tverdomed、Gerd-Volker Röschenthaler、Nataliya Kalinovich、Enno Lork、Alla V. Dogadina、Boris I. Ionin
DOI:10.1016/j.tet.2008.03.020
日期:2008.5
bisphosphonate. Their aromatization by the KMnO4–Al2O3 system affords 4-methyl and 4,5-dimethylbenzene-1,2-diphosphonates (2a, 2b), used as precursor for the generation of benzyl-type carbanions (3a, 3b) by lithiation with lithium isopropylamide in THF at −80 °C. The carbanions react with electrophilic reagents (chlorotrimethylsilane, p-fluorobenzaldehyde, and ethyl trifluoroacetate) in situ to form corresponding
碳环1,2-二膦酸酯(1a,1b)是通过经典供体碱1,3-二烯(异戊二烯和2,3-二甲基-1,3-丁二烯)与乙炔双膦酸四乙酯的Diels-Alder反应制备的。通过KMnO 4 -Al 2 O 3系统进行的芳构化可得到4-甲基和4,5-二甲基苯-1,2-二膦酸酯(2a,2b),用作生成苄型碳负离子(3a,3b)的前体。通过在-80°C下用异丙基氨基化锂在THF中锂化来完成。碳负离子与亲电子试剂(氯三甲基硅烷,p-氟代苯甲醛和三氟乙酸乙酯)原位形成高产率的相应α-取代的单烷基-和二烷基苯二膦酸酯。