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Dimetalation: The Acidity of Monometalated Arenes Towards Superbasic Reagents
Author(s) -
Baston Eckhard,
Maggi Raimondo,
Friedrich Kirstin,
Schlosser Manfred
Publication year - 2001
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200111)2001:21<3985::aid-ejoc3985>3.0.co;2-y
Subject(s) - chemistry , aniline , tetrahydrofuran , medicinal chemistry , solvent , benzene , reagent , organic chemistry , hydrocarbon
Twofold hydrogen/metal interconversions ("dimetalations") can be accomplished with “spiny” arenes ( tert ‐butylbenzene, 1,4‐di‐ tert ‐butylbenzene, 1,1,3,3‐tetramethylindane and congeners) and N , N ‐crowded anilines (2,2,6,6‐tetramethyl‐1‐phenylpiperidine and N , N ‐bis[triethylsilyl]aniline), albeit incompletely (average and optimum yields of trapping products 25% and 41%, respectively). All the evidence points at an aggregate phenomenon. Dimetalation occurs only with an excess of a highly concentrated butyllithium/potassium tert ‐butoxide mixture in hydrocarbon media. In tetrahydrofuran, no trace of a dimetalated species is found, although such species, once generated in a different manner, are moderately stable in this solvent at −75 °C. 1,4‐Dimetalloarenes are favored over the 1,3‐isomers; 1,2‐isomers do not form at all. As found by competition kinetics, 2,2,6,6‐tetramethyl‐1‐phenylpiperidine and N , N ‐bis(triethylsilyl)aniline undergo monometalation at roughly the same rate as tert ‐butylbenzene and much more slowly than benzene does.