Electrophilic substitution, aromatic deuterium exchange

Electrophilic substitution, aromatic, 31, 130-167, 381 1,2-ti. 1,4-addition, 195 as addition/elimination, 133 complexing with substituent, 160 deuterium exchange, 131,158 electronic effects in, 148, 158, 159 energetics of, 132, 136 field effect in, 152 hyperconjugation in, 153 inductive effect in, 22,152,153,156, 160... 

The intermediate tricyclic ketones 495 and 496 have been transformed to the methoxy-substituted derivative 97284,285) latter ketone is subject to hydrogen-deuterium exchange only under basic conditions and appears to exist entirely in the keto form despite the ready formation of its anion and successful methylation on oxygen . In agreement with the aromatic nature of 490, the hydrocarbon undergoes electrophilic substitution reactions... 

It is possible to replace the ring hydrogens of many aromatic compounds by exchange with strong acids. When an isotopically labeled acid such as D2S04 is used, this reaction is an easy way to introduce deuterium. The mechanism is analogous to other electrophilic substitutions ... 

Electrophilic substitution in excited-state aromatics is the subject of only one report, concerned with a photophysical investigation of hydrogen-deuterium exchange in 1-methoxynaphthalene. ... 

Because aromatic compounds are subject to electrophilic attack, D+ provides a ready entry of deuterium into the aromatic molecule. The reaction of various anhydrides with D2O is one of the most common methods for providing protic acids. The acidity of protic acids can be enhanced by co-catalysts , which are usually Lewis acids. Hence electrophilic substitutions by protic acids and Lewis acids are of primary interest in hydrogen isotope exchange. 

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