Naphthalene, 2- synthesis Friedel-Crafts reaction

Shudo and coworkers have reported that 0,0-diprotonated nitroalkenes (16) behave as novel electrophilic species which can efficiently alkylate aromatics such as benzene, anisole, chlorobenzene, naphthalene, etc. under extremely mild conditions (equation 28). The reaction enables the synthesis of a-arylated ketones (17) which are difficult to synthesize by conventional Friedel-Crafts reactions. 

A final synthetic effort in the yohimbine alkaloid area concerns the studies reported by Loewenthal and his coworkers (Scheme 3.92) (143). The aim was to develop an efficient method to prepare the bicyclic enone 21, which serves as a key intermediate in the Woodward reserpine synthesis strategy (19). The route for preparation of 21 began with Friedel Crafts reaction of 2-methoxynaphthalene (523) with the oxalyl chloride equivalent 524, a process which afforded the acenaphthenoquinone 525. Oxidative-decarboxylation of 525 yielded the naphthalene-carboxylic acid 526 which was transformed by Birch reduction and esterification to the dihydro-derivative 527. Carboxyla-tion then provided geminal diester 528 which was epoxidized. Sequential lactonization and methylation afforded tricyclic lactone 529. Ester cleavage with subsequent decarboxylation gave lactone 530 which was demethylated to provide 531. While no further effort was given to the development of this... 

Anthraquinone dyes are derived from several key compounds called dye intermediates, and the methods for preparing these key intermediates can be divided into two types (/) introduction of substituent(s) onto the anthraquinone nucleus, and (2) synthesis of an anthraquinone nucleus having the desired substituents, starting from benzene or naphthalene derivatives (nucleus synthesis). The principal reactions ate nitration and sulfonation, which are very important ia preparing a-substituted anthraquiaones by electrophilic substitution. Nucleus synthesis is important for the production of P-substituted anthraquiaones such as 2-methylanthraquiQone and 2-chloroanthraquiaone. Friedel-Crafts acylation usiag aluminum chloride is appHed for this purpose. Synthesis of quinizatia (1,4-dihydroxyanthraquiQone) is also important. 

Other Formylations. Formyl fluoride, the only known stable formic acid derivative, can be used to perform Friedel-Crafts-type acylation to form aromatic aldehydes. The method was developed by Olah and Kuhn.105 Although a number of Lewis acids may be used, BF3 is the best catalyst. It is dissolved in the aromatic compound to be formylated then formyl fluoride is introduced at low temperature and the reaction mixture is allowed to warm up to room temperature. The aldehydes of benzene, methylbenzenes, and naphthalene were isolated in 56-78% yields. Selectivities are similar to those in the Gattermann synthesis ( toiuene benzene = 34.6, 53.2% para isomer). The reacting electrophile was suggested to be the activated HCOF BF3 complex and not the free formyl cation. Clearly there is close relationship with the discussed CO—HF—BF3 system. 

There are two main synthetic routes to naphthalene the Haworth synthesis and a Diels-Alder approach. In the Haworth synthesis (Scheme 12.1), benzene is reacted under Friedel-Crafts conditions with succinic anhydride (butanedioic anhydride) to produce 4-oxo-4-phenylbutanoic acid, which is reduced with either amalgamated zinc and HCl (the Clemmensen reduction) or hydrazine, ethane-1,2-diol and potassium hydroxide (the Wolff-Kischner reaction) to 4-phenylbutanoic acid. Ring closure is achieved by heating in polyphosphoric acid (PPA). The product is 1-tetraione and reduction of the carbonyl group then gives 1,2,3,4-tetrahydronaphthalene (tetralin). Aromatization is achieved by dehydrogenation over a palladium catalyst. 

Although it is possible to synthesize anthracene in a number of ways using Friedel-Crafts methodology, the usual routes involve either an adaptation of the Haworth synthesis of naphthalene or a Dicls-Alder reaction using naphtho-l,4-quinone as the dienophile. 

The f-butylated naphthalene derivative (18 equation 49) is of interest as an intermediate for the synthesis of fungicides. Tetrahydronaphthalene derivatives, such as (20), have been evaluated as antifertility agents. Sugita et al. have studied the AlCb-catalyzed Friedel-Crafts alkylation of benzene with l-phenyl-2-propanol and 2-phenyl-1-propanol in the presence of additives, such as CuCb, CU2CI2 and decalin. Highly regioselective formation of 1,1-diphenylpropane was observed with Cu or Cu chloride as the additive. Some pertinent results of synthetic value are shown in Scheme 5. The addition of decalin diminished the alkylation reaction to give Ae reduction product 1-phenylpropane. 

The Friedel-Crafts process is frequently the most useful method for the introduction of an alkyl group. The reaction is capable of many practical applications, and a large number of patents have appeared on the preparation of alkyl derivatives of various aromatic compounds such as xylene, naphthalene, and phenols. Patents have covered the utilization of such alkylating agents as the olefins derived from cracking, the mixtures prepared by chlorination of petroleum fractions, and various naturally occurring waxy esters. The most important application is the synthesis of ethylbenzene from ethylene and benzene. 

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