RUTHENIUM-MEDIATED NUCLEOPHILIC AROMATIC SUBSTITUTION OF HALOGENS ON BENZENE SYSTEMS: SYNTHESIS OF 1,3,5-TRIAMINOBENZENES

 
 
 
 

RUTHENIUM-MEDIATED NUCLEOPHILIC AROMATIC SUBSTITUTION OF HALOGENS ON BENZENE SYSTEMS: SYNTHESIS OF 1,3,5-TRIAMINOBENZENES

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Title: RUTHENIUM-MEDIATED NUCLEOPHILIC AROMATIC SUBSTITUTION OF HALOGENS ON BENZENE SYSTEMS: SYNTHESIS OF 1,3,5-TRIAMINOBENZENES
Author: Serve', Brian J.
Description: A method for the synthesis of unsymmetrical peralkylated 1,3,5-triaminobezenes was developed. The strategy consists of sequential ruthenium-mediated nucleophilic aromatic substitution to install two secondary amines and a palladium-catalyzed amination for the third. 1,3,5-Trichlorobenzene was metallated with [(CH3CN)3RuCp]PF6 in 51% yield. It was discovered that [(CH3CN)3RuCp]PF6 is not completely consumed in the reaction and the material causes an unusual decomposition of the resulting mono-substituted Ru-complex under SNAr conditions. Recrystallization and chromatography were ineffective at removing [(CH3CN)3RuCp]PF6; however, it was discovered that acetone destroys the precursor leaving (1,3,5-trichlorobenzene)RuCpPF6 intact. Two sequential nucleophilic aromatic substitution reactions were performed using the non-coordinating solvent, methylene chloride, and the heterogeneous base, sodium carbonate. It was found that SNAr conditions would not substitute the third chloro group. With each successive substitution the Ru-complex becomes less reactive towards SNAr requiring higher temperatures as forcing conditions, which prematurely decomplexes the arene. The synthesis was completed by photolytically cleaving the metal and performing a palladium-catalyzed amination on the final chloro group. The method successfully synthesized 1,3,5-tripyrrolidinobenzene and unsymmetric 1-morpholino-3-piperidino-5-pyrrolidinobenzene in 23% yield over five steps for the latter.
Permanent Link: http://rave.ohiolink.edu/etdc/view?acc_num=case1152813193
http://hdl.handle.net/2374.OX/16481
Date: 2006

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