Tetralones reduction

An interesting route to generate type I aziridines which is formally the formation of bond b is shown in Equation (5) <2002BML3141>. Oxime 21 is prepared in high yield from the corresponding tetralone. Reduction of oxime 21 with LiAlH4 and diethylamine in tetrahydrofuran (THE) provides the unprotected type I aziridine 22 in good yield. 

Examples of palladium-catalyzed reduction are 4-chloro-2,6-di-r-butyl-phenol to 2,6-di-t-butylcyclohexanone (750 psig, 25 C) with loss of halogen 24), 1,8-dihydroxynaphthalene to 8-hydroxy-1-tetralone 30), and 2,4-dimethylphenol to 2,4-dimethylcyclohexanone (27). 

A number of products in which one of the naphthalene rings has been reduced have interesting pharmacological properties. Reaction of tetralone 30 with dimethylamine under TiCl catalysis produces the corresponding enamine (31). Reaction with formic acid at room temperature effects reduction of the... 

Autoxidation may in some cases be of preparative use thus reference has already been made to the large-scale production of phenol+ acetone by the acid-catalysed rearrangement of the hydroperoxide from 2-phenylpropane (cumene, p. 128). Another example involves the hydroperoxide (94) obtained by the air oxidation at 70° of tetrahydro-naphthalene (tetralin) the action of base then yields the ketone (a-tetralone, 95), and reductive fission of the 0—0 linkage the alcohol (a-tetralol, 96) ... 

Johnson has developed two linear approaches to synthesize the C-nor-D-homosteroid skeleton (Scheme 2.2). In his first approach [21], tetralone 19, obtained from reduction of 2,5-dimethoxynaphthalene, was used as the source of the C,D-rings. The B- and A-rings were constructed by sequential Robinson annulations (19 —> 20 —> 21). The Cl 1,12 olefin was then introduced to provide 22. Ozonolysis of 22 followed by an aldol reaction of the resulting dialdehyde gave 23. Subsequent deformylation and deoxygenation afforded the cyclopamine skeleton 24. 

The use of such an oxazaborolidine system in a continuously operated membrane reactor was demonstrated by Kragl et /. 58] Various oxazaborolidine catalysts were prepared with polystyrene-based soluble supports. The catalysts were tested in a deadend setup (paragraph 4.2.1) for the reduction of ketones. These experiments showed higher ee s than batch experiments in which the ketone was added in one portion. The ee s vary from 84% for the reduction of propiophenone to up to >99% for the reduction of L-tetralone. The catalyst showed only a slight deactivation under the reaction conditions. The TTON could be increased from 10 for the monomeric system to 560 for the polymer-bound catalyst. 

Tetralone oxime, reduction with lithium aluminum hydride, 48, 23... 

The preparation of 6-methoxy-2-naphthol is of particular interest as the starting point in many synthetic sequences. It is readily converted to 6-methoxy-2-tetralone through a Birch reduction... 

Partial reduction of naphthols was accomplished by sodium in liquid ammonia. In the absence of alcohols small amounts of 5,8-dihydro-a-naphthol or 5,8-dihydro- -naphthol were isolated. In the presence of tert-amyl alcohol, a-naphthol gave 65-85% yield of 5,8-dihydro-a-naphthol while -naphthol afforded 55-65% of -tetralone [399] Procedure 26, p. 211). Lith-... 

As noted earlier, most classical antidepressant agents consist of propylamine derivatives of tricyclic aromatic compounds. The antidepressant molecule tametraline is thus notable in that it is built on a bicyclic nucleus that directly carries the amine substituent. Reaction of 4-phenyl-l-tetralone (18) (obtainable by Friedel-Crafts cyclization of 4,4-diphenyl butyric acid) with methyl amine in the presence of titanium chloride gives the corresponding Schiff base. Reduction by means of sodium borohydride affords the secondary amine as a mixture of cis (21) and trans (20) isomers. The latter is separated to afford the more active antidepressant of the pair, tametraline (20). 

Tetralone has been prepared by a variety of methods, but the only practical procedures are relatively recent ones involving reduction of /9-naphthyl methyl ether with sodium and alcohol2 or with sodium and liquid ammonia,3 high-pressure catalytic hydrogenation of /9-naphthol,4 or catalytic oxidation of 2-tetralol by hydrogen transfer with ethylene.6... 

A modified oxazaborolidine 2 catalyzing the enantioselective reduction of acetophenone or tetralone with borane proved to give ttn values in the same order of magnitude [10, 11]. Using a special hydroxyproUne-based polymer-enlarged oxazaborolidine 3, a ttn of 1400 for the reduction of tetralone was achieved (Fig. 3.1.3, 3) [5, 12]. 

Tetralone 31 could also be synthesized much more efficiently by employing a chemoselective ketone reduction of 32 to give the lactone 33. A double Friedel-Crafts alkylation/acylation sequence employing a variety of Lewis or protic acids and benzene gave the tetralone 31 directly. Triflic acid and HF produced the highest yields of tetralone, presumably through the intermediacy of the diaryl acid 34 (Scheme 6)... 

Quallich and Woodall described the first asymmetric synthesis utilizing a catalytic enantioselective reduction of the ketoester 35 with (S)-terahydro-l-methyl-3,3-diphenyl-lH,3W-pyrrolo[l,2-c][l,3.2]oxazaborole (CBS) to give the desired hydroxyester 36 (90% ee). After mesylation, Sn2 displacement with a higher-order cuprate derived from copper cyanide gave the diaryl r-butyl ester 37 with good chirality transfer. Intramolecular Friedel-Crafts cyclization gave the tetralone 31 in 90% ee (Scheme 7). ... 

Sertraline is the active pharmaceutical ingredient (API) in Pfizer s antidepressant Zoloft [25]. The developed commercial process employs an SMB chromatographic resolution of tetralone (Scheme 13.10) in >99% ee followed by diastereoselective reductive amination to give 95% sertraline (cis-isomer) and 5% trans-isomer the (4R)-tetralone can be racemized with an alkoxide base [8]. Asymmetric processes to sertraline have been described [26]. Our studies started with the original patented process involving palladium-catalyzed reductive amination of a tetralone to give a mixture of 80% racemic-cis and 20% racemic-trans diastereomers [27]. The cis-diastereomer can be purified by selective crystallization from toluene followed by diastereomeric crystallization of the (lS,4S)-enantiomer using (R)-... 

The iV-aminopyrrole - benzene ring methodology has been applied to a synthesis of the 9,10-dihydrophenanthrene juncusol (218) (81TL1775). Condensation of the tetralone (213) with pyrrolidine and reaction of the enamine with ethyl 3-methoxycarbonylazo-2-butenoate gave pyrrole (214). Diels-Alder reaction of (214) with methyl propiolate produced a 3 1 mixture of (215) and its isomer in 70% yield. Pure (215) was reduced selectively with DIBAL to the alcohol, reoxidized to aldehyde, and then treated with MCPBA to generate formate (216). Saponification to the phenol followed by O-methylation and lithium aluminum hydride reduction of the hindered ester afforded (217), an intermediate which had been converted previously to juncusol (Scheme 46). 

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