Koner Abhishek, Serin Spencer C, Schnakenburg Gregor, Patrick Brian O, Gates Derek P, Streubel Rainer
Institut für Anorganische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Straße 1, D-53121 Bonn, Germany.
Dalton Trans. 2017 Aug 8;46(31):10504-10514. doi: 10.1039/c7dt01859b.
Backbone (R'N)P-substituted imidazole-2-thiones 2a-c [(R'N)P-IMS; IMS = 1,3-dialkylimidazole-2-thione-4-yl, a: R = Pr, R' = Et; b: R = Mes, R' = Et, c: R = Me, R' = Pr] were treated with PCl to synthesize R'N(Cl)P-substituted imidazole-2-thiones 3a-c [R'N(Cl)P-IMS]. The P-chloro compounds 3a,b were used to explore the chemistry further, i.e. nucleophilic substitution at phosphorus using PhCHLi or fluorenyl lithium afforded compounds 4a-c [R'N(R'')P-IMS; a: R = Pr, R' = Et, R'' = PHCH; b: R = Mes, R' = Et, R'' = Flu c: R = Pr, R' = Et, R'' = Flu]. Compound 4c was used to access the P-borane adduct 5 [R'N(R'')(BH)P-IMS; R = Pr, R' = Et, R'' = Flu] and phosphinoyl-substituted imidazolium hydrogensulfate 6 [[R'N(R'')(O)P-IMH]HSO; IMH = 1,3-dialkylimidazolium-4-yl, R = Pr, R' = Et, R'' = Flu]. Compounds 4a,b were transformed into the P-Cl compounds 7a,b [R''(Cl)P-IMS; a: R = Pr, R'' = PhCH; b: R = Mes, R'' = Flu] which represent potential starting materials for backbone phosphaalkenyl substituted imidazole-2-thiones. Compound 7a yielded the NHC-stabilized phosphenium salt 8 [[R''(IMe)P-IMS]Cl; R = Pr, R' = Et, R'' = PhCH, IMe = 1,3,4,5-tetramethylimidazole-2-ylidene] in reaction with 1,3,4,5-tetramethylimidazole-2-ylidene (IMe). Attempts to deprotonate 7a,b using BuLi revealed that nucleophilic substitution of P-Cl to give the P-Bu product occurred preferentially, and dehydrochlorination to the phosphaalkene was not observed.
