An easy access to trisubstituted vinyl chlorides and improved synthesis of chloro/bromostilbenes
作者:C Muthiah、K.Praveen Kumar、Sudha Kumaraswamy、K.C Kumara Swamy
DOI:10.1016/s0040-4020(98)00886-2
日期:1998.11
the bromostilbenes ArCH=CBr(C6H4-4-R) can be prepared in significantly higher yields than by using NaH. The stereochemistry of two of the trisubstituted vinyl chlorides is unambiguously proven by X-ray structure determination. Thus for (Cl)PhC=CPh(Me), the isomer with the upfield NMR shift for the CH3 protons and for (Cl)PhC=C(Ph)(C6H4-4-Me), the isomer with the downfield NMR shift for the -C6H4-4-CH3
α-氯膦酸酯(OCH 2 CMe 2 CH 2 O)P(O)CHCl-C 6 H 4 -4-R [R = H(4),Me(5),OMe(6)],现在很容易在NaH存在下与酮R'C(O)R''反应(无需使用更昂贵的t- BuLi),得到三取代的乙烯基卤化物R'C(R'')= CCl(C 6 H 4 -4 -R),产量高。相应的α-bromophosphonates [R = H(7)中,Me(8)]无法与酮反应,得到对称的乙炔4-RC 6 H ^ 4 -CCC 6H 4 -4-R为可分离的产物,收率低。我们已经发现,回流的二甲苯中的K 2 CO 3是合成氯代苯乙烯的良好基础。使用该碱,与使用NaH相比,可以显着更高的收率制备溴化萘苯甲烷ArCH = CBr(C 6 H 4 -4-R)。通过X射线结构测定清楚地证明了两个三取代的氯乙烯的立体化学。因此,对于(Cl)PhC = CPh(Me),对于C