AROMATIC CYCLODEHYDRATION. XXI. ortho- AND para-(9-ANTHRYL)BENZOIC ACIDS¹

Rapid Defunctionalization of Carbonyl Group to Methylene with Polymethylhydrosiloxane−B(C6F5)3

“…The hydroxyl group can be removed by a Barton−McCombie procedure, wherein highly malodorous xanthate and Bu 3 SnH are required. Some other methods known in the literature include catalytic hydrogenation and reaction involving use of PtO 2 , HI−phosphorus, BH 3 , Zn/HCl/HgCl 2 /H 2 O, NaBH 4 −CF 3 CO 2 H, NaCNBH 3 −BF 3 Et 2 O, LAH−AlCl 3 , Et 3 SiH−BF 3 Et 2 O or CF 3 CO 2 H besides a few others . The majority of the known procedures used for defunctionalization are nonchemoselective and require harsh reaction conditions.…”

Synthesis and Optoelectronic Properties of Hexahydroxylated 10‐O‐R‐Substituted Anthracenes via a New Modification of the Friedel–Crafts Reaction Using O‐Protected ortho‐Acetal Diarylmethanols

“…iii) protection of the hydroxyl group in 7 or 8 with an alkyl or arylalkyl halide to obtain protected diarylmethanols 9 or 10, iv) acid-driven cy-A C H T U N G T R E N N U N G clization of 9 or 10 to the corresponding anthracene systems 3 a-e (Scheme 2 and Scheme 3). The last step is a Friedel-Crafts type reaction and resembles its later intramolecular modification known as the Bradsher re- [26][27][28] Our modification of this reaction differs from the previous examples in that it employs reactants bearing two functional groups, acetal and dibenzyl alkoxy, which are acid sensitive and, as mentioned, have not been used together before. Therefore, this modified reaction is much more vulnerable to changes of reaction conditions than its original versions and hence required tuning which is also described below.…”

“…anols via free aldehydes to anthracenes, as in the Bradsher reaction of o-formyl diarylmethanes. [26,27] Thus, the reaction of the diarylmethanol 9 a with Amberlyst 15 in acetone afforded after 4 h the aldehyde 11 a in 96 % yield, while after 24 h the anthracene 3 a was isolated in 43 % yield (Scheme 5, pathway i and ii). The anthracene 3 a was also the main product of the reaction of the aldehyde 11 a (obtained in an independent way) with Amberlyst 15 in acetone (Scheme 4, pathway iii).…”

Polymethylhydrosiloxane reduction of carbonyl function catalysed by titanium tetrachloride

“…However, the drastic reaction conditions of both processes have given rise to various other methods, all in an effort to find milder reaction conditions. Some of the alternative methods include catalytic hydrogenation [4][5], reductions using Raney nickel in hydroxide media [6], reductions using PtO 2 [7], HI-phosphorus [8][9], NaBH 4 -CF 3 COOH [10][11], NaCNBH 3 -BF 3 Et 2 O [12], LAH-AlCl 3 [13]. While these methods offer some advantages, they also suffer from some disadvantages.…”