Bradsher reagent

Bouveault-Blanc reduction, modified 16, 89 Bouveault-Locquin synthesis, improved 16, 230 Bradsher reagent 5, 642 V. Braun reaction 17, 625 Bridges s. a. Ethenylene bridges, Ring —... 

Isoquinolinium 369 and [2,7]naphthyridin-2-ium 371 salts have also been used for the preparation of 2,3,8,8a-tetrahydro-57/-oxazolo[3,2-tf]pyridine derivatives (Scheme 98) addition of Grignard reagents to 369 is followed by a spontaneous cyclization to 370 <1998JOC1767> while an asymmetric version of the Bradsher cycloaddition between 371 and chiral enol ether 372 gives 373 in good yield and selectivities <1996TL7019>. 

W. E. Parham, C. K. Bradsher, Aromatic Organolithium Reagents Bearing Electrophilic Groups. Preparation by Halogen-Lithium Exchange, Acc. Chem. Res. 1982, 15, 300. 

Cychdehydration. The sulfonic acid resin Ambcrlite-15 was found to be more satisfactory than Bradsher s reagent (2, 214), sulfuric acid, or formic acid for cyclo-dehydration of 2-methyl-4-phenyl-2-butanol (1) to 1,1-dimethylindane (2). ... 

Bradsher et found that treatment of the 1 l//-pyrido[2,l-i>]quinazo-lin-1 l-one 286 with excess organolithium reagent gave the tertiary carbinol 324. 

Bradsher s reagent was found to be superior to PPA or a mixture of sulfuric acid-phosphoric acid for cyclodehydration of /1-hydroxy ketones of the type (4).21... 

As a synthetic method the Bradsher reaction per se appears to be superior to the Elbs reaction. The direct procedure of Meth-Cohn uses carcinogenic n-butyl dichloromethyl ether. The Castle procedure is relatively free of toxic reagents, isomeric precursors, and rearrangements, but numerous steps are involved before the Bradsher reaction is reached. Thus, all of these methods have advantages and shortcomings. 

Early reports from the Bradsher group highlighted new routes to anthracene derivatives iP In the event, conversion of chloride 49 to ketone 6 was accomplished by treatment with cuprous cyanide followed by 1,2-addition of a Grignard reagent. The cyclized product 7 was obtained by heating with hydrobromic acid. It was reported later that liquid sulfur dioxide as solvent was effective in facilitating the aromatic cyclodehydration. " ... 

Yamato and co-workers introduced dichloromethyl methyl ether in the presence of titanium tetrachloride as a reagent for one-pot formylation followed by in situ Bradsher cyclization. In this way anthracene regioisomers 25 and 26 were obtained from diaryImethane 24 in good yield. The initially formed anthracene derivative presumably reacts with excess dichloromethyl methyl ether to yield 9- or 10-formylanthracene derivative 25 or 26. 

A soln. of 4-hydroxy-4-methyl-5-phenyl-2-pentanone in 48%-HBr-glacial acetic acid heated 2 hrs. on a steam bath 1,3-dimethylnaphthalene. Y 87-90%. -The above mixture of HBr and acetic acid (Bradsher s reagent) gave higher yields than other acids. F. e. s. P. Ganonne, P. Holm, and L. G. Leitch, Gan. J. Ghem. 45, 2151 (1967). 

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