ChemInform Abstract: HALOGENATION OF AROMATIC SILANES. XXIX. PREPARATION OF CHLORO AND BROMO DERIVATIVES OF 2,5‐DIMETHYLPHENYLTRICHLOROSILANE

Abstract

Die aus Brom‐p‐xylol (I) erhältliche Grignardverbindung (II) reagiert mit Tetrachlorsilan zum 2,5‐Dimethylphenyl‐trichlorsilan (III).

Preparation of Tyrian Purple (6,6′-Dibromoindigo): Past and Present

“…The 2,4-dibromobenzoic acid ( 67 ) required in this procedure is usually prepared via the hydrolysis of 2,4-dibromobenzonitrile ( 71 ) [ 147 , 148 , 149 , 150 , 151 , 152 , 153 , 154 , 155 , 156 ] or by the oxidation of 2,4-dibromotoluene ( 45 ) [ 157 , 158 , 159 , 160 , 161 , 162 , 163 , 164 , 165 , 166 , 167 ]. Unfortunately, neither of these methods is particularly attractive.…”

“…2,4-Dibromotoluene ( 75 ) is also a potential precursor for 2,4-dibromobenzoic acid ( 67 ). The former is usually prepared by multistep procedures [ 157 , 159 , 160 , 161 , 162 , 163 , 164 , 167 , 169 , 170 , 171 ], [for example, from 4-nitrotoluene ( 72 ) [ 160 , 164 , 170 ] ( Scheme 22 )], since direct bromination of 4-bromotoluene ( 20 ) ordinarily gives an 7:1 mixture of 75 and 3,4-dibromotoluene ( 76 ) [ 158 , 160 ] ( Scheme 23 ).…”

“…Condensations of 4-bromo-2-chlorobenzoic acid ( 90 ) with aniline [ 220 ] and with p -anisidine [ 221 ] have likewise been reported to give products in which the ortho chlorine atom is replaced by the amino nucleophile. All known preparative syntheses of acid 90 are based on the oxidation of 4-bromo-2-chlorotoluene ( 89 ) [ 221 , 222 , 223 , 224 ]. This, in turn, has been made by multistep procedures, either from 4-amino-2-nitrotoluene ( 11) ( Scheme 30 ) [ 222 , 223 ] or from p -nitrotoluene ( 72 ) in a fashion analogous to the synthesis of the dibromotoluene 75 above (Scheme31)[ 225 , 226 ].…”