Chlorophosphonates: Inexpensive Precursors for Stereodefined Chloro-Substituted Olefins and Unsymmetrical Disubstituted Acetylenes
摘要:
New chlorophosphonates bearing a 1,3,2-dioxaphosphorinane ring which are useful for the stereospecific synthesis of 5-chlorofurfuryl substituted olefins and chloro-substituted dienes have been obtained by an easy, inexpensive route. The utility of some of these in the synthesis of ferrocenyl- and anthracenyl-substituted unsymmetrical acetylenes has been explored. The structures of the phosphonates (OCH2CMe2CH2O)P(O)CH2(C4H2ClO) (4) and (OCH2Me2CH2O)P(O)-(CH=CHCH(Cl)Ph (7) have been determined; in addition, the stereochemistry of (5-chlorofurfuryl)-CH=CH(4-ClC6H4) (13b) and 2,4-Cl2C6H3-CH=CH-CH=C(Ph)Cl (14a) is unambiguously proved by the X-ray structure determination.
the bromostilbenes ArCH=CBr(C6H4-4-R) can be prepared in significantly higher yields than by using NaH. The stereochemistry of two of the trisubstitutedvinylchlorides 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
A new clomiphene metabolite, extremely useful for doping analysis, was synthesized in 19% overall yield. The approach involved a Grignard reaction via a N-acylbenzotriazole intermediate to afford a key aromatic ketone and a HWE reaction. Both stereoisomers were separated and identified.
A convenient route to aryl substituted chloro and bromo olefins
作者:Sudha Kumaraswamy、K.C.Kumara Swamy
DOI:10.1016/s0040-4039(97)00277-3
日期:1997.3
A wide range of aryl substitutedchloro and bromo olefins has been prepared by treating α-chloro and α-bromophosphonates derived from 1-hydrido-5,5-dimethyl-1,3,2-dioxaphosphorinane with sodium hydride in THF at 0°C followed by an aldehyde.
reaction of inexpensive α-chlorophosphonates with alkyl acrylates in the presence of sodium hydride is reported. Reaction with dimethylmaleate or fumarate also leads to cyclopropyl-substituted phosphonates. These reactions take place via Michaeladdition of acrylate, dimethylmaleate, or fumarate to the phosphonate carbanion, followed by expulsion of the chloride ion.