Studium kinetiky a mechanismu sulfurizace P(III) sloučenin deriváty 1,2,4-dithiazolu

Mgr. Oleksandr Ponomarov

Doctoral thesis

Study of kinetics and mechanism of sulfurization of P(III) compounds with 1,2,4-dithiazole derivatives

Abstract:

T.inact novych substituovanych 5-fenylthio- and 5-fenoxy-1,2,4-dithiazol-3-on. a .est 4- fenyl-1,2,4-dithiazolidin-3,5-dion. bylo v pr.m.rnych a. dobrych vyt..cich (53.76%) p.ipraveno z odpovidajicich S- a O-fenyl thiokarbamat. a chlorkarbonylsulfenylchloridu v suchem etheru p.i .10 ??C. V.echny p.ipravene slou.eniny byly charakterizovany NMR spektry, elementarni analyzou a n.ktere i rentgenostrukturni analyzou. Ostatni, ji. d.ive zname derivaty 1,2,4-dithiazolu byly p.ipraveny podle literatury. V dal.i .asti prace byla testovana sulfuriza.ni aktivita celkem dvaceti p.ti p.ipravenych 5- substituovanych-1,2,4-dithiazol-3-on. a 3-thion. a sedmi 4-(subst.fenyl)-1,2,4-dithiazolidin- 3,5-dion. v..i trifenyl-fosfitu v acetonitrilu, dichlormethanu, tetrahydrofuranu a toluenu p.i 25 ??C. Bylo zji.t.no, .e v.echny p.ipravene 1,2,4-dithiazoly jsou mnohem lep.i sulfuriza.ni .inidla ne. komer.n. dostupne slou.eniny (tj. bis(fenylacetyl)disulfid, tetraethylthiuramdisulfid, Beaucageovo .inidlo a elementarni sira). Ve v.ech rozpou.t.dlech se jako neju.inn.j.i ukazaly 5-fenoxy, 5-fenylthio a 5-ethoxy-1,2,4-dithiazol-3-on, jejich. reaktivita je nejmen. stokrat vy..i ne. u ostatnich 1,2,4-dithiazol. a o dal.ich n.kolik .ad. vy..i ne. u komer.n. dostupnych .inidel. V rozporu s p.edchozimi publikovanymi vysledky jinych autor. sulfurizace s 3-ethoxy-1,2,4-dithiazol-5-onem neposkytuje karbonylsulfid a ethylkyanat jako vedlej.i produkt, av.ak vznika nestabilni ethoxythiokarbonylisokyanat, ktery byl zachycen reakci s 4-methoxyanilinem. Podobne experimenty prokazaly, .e mistem ataku 1,2,4,-dithiazoloveho skeletu je u 5-fenoxy a 5-fenylthio derivat. atom siry vedle karbonylove skupiny. Reak.ni mechanismus zahrnuje rychlost ur.ujici atak atomu fosforu na atom siry (nukleofilni substituce na si.e), po kterem nasleduje rozklad vznikleho fosfonioveho intermediatu na odpovidajici thiofosfat a isokyanat resp. isothiokyanat. Existence fosfonioveho intermediatu v pr.b.hu sulfurizace trifenylfosfinu 5-fenyl-1,2,4-dithiazol-3- thionem byla prokazana na zaklad. kineticke studie. Z Hammettovy a Bronstedovy korelace a z dal.ich kinetickych m..eni bylo zji.t.no, .e struktura tranzitniho stavu je tem.. nepolarni u nejreaktivn.j.ich derivat. 1,2,4-dithiazolu, kde.to polarn.j.i tranzitni stav .aste.n. podobny fosfoniovemu intermediatu je realitou u malo reaktivnich 1,2,4-dithiazol.. Rozsah vytva.eni vazby P.S spolu se .t.penim vazby S.S je velmi podobny ve v.ech reak.nich seriich . pouze postupn. klesa s rostouci reaktivitou p.islu.neho 1,2,4-dithiazolu. 4-(Subst.fenyl)-1,2,4-dithiazolidin-3,5-diony, jsou mnohem men. u.innymi sulfuriza.nimi .inidly. Studium mechanismu sulfurizace ukazalo, .e u t.chto derivat. je tranzitni stav reakce velmi polarni a jeho struktura se bli.i struktu.e obojetneho fosfonioveho intermediatu.

Abstract:

Thirteen new substituted 5-phenylthio- and 5-phenoxy-1,2,4-dithiazole-3-ones and six 4- phenyl-1,2,4-dithiazolidine-3,5-diones were prepared in modest yields (53?76%) from corresponding S- and O-phenyl thiocarbamates and chlorocarbonylsulfenyl chloride. All of the compounds were characterized by NMR and elemental analysis and some of them by Xray diffraction. Other known 1,2,4-dithiazole derivatives were prepared according to the literature. The sulfurization efficiency of twenty five 5-substituted-1,2,4-dithiazole-3-ones and 3-thiones and seven 4-(subst.phenyl)-1,2,4-dithiazolidine-3,5-diones towards triphenyl phosphite in acetonitrile, dichloromethane, tetrahydrofuran and toluene at 25 °C was evaluated. All the 1,2,4-dithiazoles are much better sulfurizing reagents than commercially available agents (phenylacetyldisulfide, tetraethylthiuramdisulfide, Beaucage?s reagent and elemental sulfur). The most efficient sulfurizing agents in all solvents are 3-phenoxy, 3-phenylthio and 3- ethoxy-1,2,4-dithiazole-5-one whose reactivity is at least two orders of magnitude higher than that of other 1,2,4-dithiazoles. Contrary to a previous report, the sulfurization with 3-ethoxy- 1,2,4-dithiazole-5-one does not provide carbonylsulfide and ethyl cyanate as the additional reaction products but unstable ethoxythiocarbonyl isocyanate which has been trapped with 4- methoxyaniline. Similar trapping experiments have proven that the site of attack is at the sulfur adjacent to the C=O group for 3-phenoxy and 3-phenylthio compounds. The reaction pathway involves rate-limiting initial nucleophilic attack of the phosphorus at sulfur followed by decomposition of the phosphonium intermediate to the corresponding phosphorothioate and isocyanate/isothiocyanate species. The existence of the phosphonium intermediate during sulfurization of triphenyl phosphine with 3-phenyl-1,2,4-dithiazole-5-thione was proven using kinetic studies. From the Hammett and Brřnsted correlations and from other kinetic measurements it was concluded that the transition-state structure is almost apolar for the most reactive 1,2,4-dithiazoles whereas a polar structure resembling a zwitter-ionic intermediate may be more appropriate for the least reactive 1,2,4-dithiazoles. The extent of P?S bond formation and S?S bond cleavage is very similar in all reaction series but it gradually decreases with the reactivity of the 1,2,4-dithiazole derivatives. 4-(Subst. phenyl)-1,2,4-dithiazolidine-3,5-diones, are much less effective sulfurizing agents. The study of sulfurization mechanism showed that the transition state is very polar and its structure is very close to the zwitter-ionic intermediate.

Keywords

Kinetika, mechanismus, sulfurizace, 1, 2, 4-dithiazoly

Language used: Czech

Date on which the thesis was submitted / produced: 20. 12. 2012

Accessible from:: 31. 12. 2999

Thesis defence

• Date of defence: 28. 2. 2013

University of Pardubice

Faculty of Chemical Technology

Doctoral programme / field:
Organic Chemistry / Organic Chemistry