Synthesis of amidines and amidinates with m-terphenyl substituents
LE3 .A278 2001
Master of Science
Sterically demanding amidines, 'N,N''-diisopropyl-2,4,6-triphenylbenzam idine 2.6a, and 'N,N''-dicyclohexyl-2,4,6-triphenylbenza midine 2.6b, have been prepared via reaction of the corresponding carbodiimide with 2,4,6-triphenylphenyllithium (generated 'in situ via' lithiation of 2,4,6-triphenylbromobenzene). In addition, the 'bis'-amidine derivatives 2.7 (a,b) were also prepared. The terphenyl group on the central carbon of the N-C=N system provides steric protection in the plane of the amidinate ligand and perhaps more importantly, above and below the amidine plane. Hence, the dialkylaluminum amidinate complexes 2.8a and 2.8b (prepared by reacting the 'mono'-amidines with Al(CH3)3) are resistant to hydrolysis for a considerable amount of time in their crystalline state. The 'mono'-amidines, ' bis'-amidines, and the aluminum amidinate complexes have been comprehensively characterized by spectroscopic methods and in most cases by X-ray crystallographic analysis. 'm'-Terphenyls were prepared by two methods.The first method was the reaction of trihalobenzene derivatives with Grignard reagents that proceeds 'via' an aryne intermediate. This was used to prepare the terphenyls 2.4 (a,b,c). The second method used to prepare the terphenyl 2.5 proceeds 'via' an electrophilic aromatic substitution reaction of a triphenylbenzene. Two terphenyl derivatives, 2.4 (b,c), were characterized by X-ray crystallography and these exhibit unique [CH3I] interactions.
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