近年來(lái)由于對(duì)環(huán)境保護(hù)越來(lái)越重視，一類新的硝化方法發(fā)展了起來(lái)。這種方法用鑭系金屬 lanthanide(III)或 IV 族金屬的三氟磺酸鹽 [Ln(OTf)3, Ln=La-Lu; M(OTf) 4, M= Hf, Zr] 以及 tris(trifluoromethanesulphonyl)methides("triflides") [M(CTf3) 3; M=Yb, Sc] 作催化劑【a. Waller, F. J.;Barrett, A. G. M.; Braddock, D. C.; Ramprasad, D. Chem. Commun. 1997,613. b. For an interesting report utilizing La(NO3)3/HCl/NaNO3 for thenitration of phenols see: Ouertani, M.; Girard, P.; Kagan, H. B. TetrahedronLett. 1982, 23, 4315. c. Waller, F. J.; Barrett, A. G. M.;Braddock, D. C.; Ramprasad, D. Tetrahedron Lett. 1998, 39,1641.】，催化等當(dāng)量的硝酸（69％）硝化苯環(huán)，這種方法對(duì)一般的苯環(huán)及一些鈍化的苯環(huán)都能得到高產(chǎn)率。由于只用等當(dāng)量的硝酸，所以副產(chǎn)物僅僅是水，沒(méi)有廢酸產(chǎn)生，而且催化劑可以回收，并經(jīng)過(guò)簡(jiǎn)單處理后反復(fù)使用。因此這種方法是較為環(huán)保的一種方法。
Nitric acid (69%; 274 mg, 3.0 mmol) was added to a stirredsuspension of ytterbium(III) triflate (186 mg, 0.30 mmol) in 1,2-dichloroethane(5 mL). The suspension dissolved to give a two phase system in which theaqueous phase was the more dense. Toluene(270 mg, 3.0 mmol) was added and the stirredmixture was heated at reflux for 12 h. Duringthe reaction a white solid precipitated and the organic phase became yellow,and after 12 h no phase boundary was apparent. The solution was allowed to cool and dilutedwith water. The yellow organic phase was dried (MgSO4) and evaporated to give nitrotoluene (390 mg, 95%). Thecolourless aqueous phase was evaporated to give ytterbium(III) triflate as a whitefree-flowing solid (183 mg, 98%).
本文非原創(chuàng)內(nèi)容，版權(quán)歸原作者所有。
