Rearrangements salts

The reaction of //-a/w-y-bromocrotonaldehyde with triphenylphosphine in ether gave (3-formylallyl)triphenylphosphonium bromide (78) while y-bromo-j8-methylcrotonaldehyde gave the rearranged salt (79). 

With acid, the jS-lactam (30) undergoes cleavage and re-closure to give the rearranged salt (31 A similar rearrangement occurs with sodium methoxide or sodium cyanide in methanol. Some EHMO and CNDO calculations of the optical rotatory properties of j8-lactam structures have been reported. 

Interestingly, similar rearranged salts, like hydrazinium azide hydrazi-nate [N2H5+]-[N3 ]-N2H4, have been reported by heating equimolar amounts of hydrazinium azide and hydrazine. This mixture is heated to 50 °C in an evacuated vessel for 2 days and the product obtained is recrystallized from methanol [7]. 

Mono-substituted and unsymmetrical di-substituted ureas may be prepared by a modification of Wohler s urea synthesis, salts of primary or secondary amines being used instead of the ammonium salt for interaction with potassium cyanate. Thus when an aqueous solution containing both aniline hydrochloride and potassium cyanate is heated, aniline cyanate is first formed, and then C,HjNH,HCl -h KCNO = C,H6NHj,HCNO -h KCl C,HsNH HCNO = C.H NHCONH, by the usual molecular rearrangement is converted into monophenyburea. 

When benzii is heated with potassium hydroxide solution, it undergoes a molecular rearrangement with the formation of the potassium salt of benzilic acid, or diphenyl lycollic acid ... 

Salts of primary aromatic amines react with solutions of alkali cyanates to yield first the amine cyanate, which then undergoes molecular rearrangement to the arylurea, for example ... 

Benzil (and other a-diketones Ar—CO—CO—Ar) upon refluxing with aqueous-alcoholic potassium hydroxide undergo the beozilic acid rearrangement. Thus benzil is converted into a salt of benzilic acid ... 

Preheat a water bath on the stove (or wherever) to about 80C and place the stainless steel mixing bowl in it. Once the temperature of the solution hits about 65C, take the bowl out and set aside while stirring all the while. This is where it rearranges, and the reaction is exothermic enough to sustain it s temperature nicely. If you find the temperature climbing past 80C, immerse the bowl into some cold waiter briefly. After about 15 minutes the temperature will start to fall, at which point you should transfer the whole mess to the distilling flask. Before you continue you need to choose whether you want to make the hydrochloride salt or the aqueous solution of Methylamine, though. 

Two efficient syntheses of strained cyclophanes indicate the synthetic potential of allyl or benzyl sulfide intermediates, in which the combined nucleophilicity and redox activity of the sulfur atom can be used. The dibenzylic sulfides from xylylene dihalides and -dithiols can be methylated with dimethoxycarbenium tetrafiuoroborate (H. Meerwein, 1960 R.F. Borch, 1968, 1969 from trimethyl orthoformate and BFj, 3 4). The sulfonium salts are deprotonated and rearrange to methyl sulfides (Stevens rearrangement). Repeated methylation and Hofmann elimination yields double bonds (R.H. Mitchell, 1974). 

Diallylsulfonium salts undergo intramolecular allylic rearrangement with strong bases to yield 1,5-dienes after reductive desulfurization. The straight-chain 1,5-dienes may be obtained by double sulfur extrusion with concomitant allylic rearrangements from diallyl disulfides. The first step is achieved with phosphines or phosphites, the second with benzyne. This procedure is especially suitable for the synthesis of acid sensitive olefins and has been used in oligoisoprene synthesis (G.M. Blackburn, 1969). 

If a bromomethyl- or vinyl-substituted cyclopropane carbon atom bears a hydroxy group, the homoallyiic rearrangement leads preferentially to cyclobutanone derivatives (J. Sa-laun, 1974). Addition of amines to cydopropanone (N. J. Turro, 1966) yields S-lactams after successive treatment with tert-butyl hypochlorite and silver(I) salts (H.H. Wasserman, 1975). For intramolecular cyclopropane formation see section 1.16. 

Synthesis of (A) started with the combination of 2,4,6-trimethylphenol and allyl bromide to give the or/Ao-allyl dienone. Acid-catalyzed rearrangement and oxidative bydroboration yielded the dienone with a propanol group in porlactone ring were irons in the product as expected (see p. 275). Treatment with aqueous potassium hydroxide gave the epoxy acid, which formed a crystalline salt with (R)-l-(or-naphthyl)ethylamine. This was recrystallized to constant rotation. 

Gassman and co-workers developed a synthetic route from anilines to indoles and oxindoles which involves [2.3]-sigmatropic rearrangement of anilinosul-fonium ylides. These can be prepared from Ai-chloroanilines and ot-thiomcthyl-ketones or from an aniline and a chlorosulfonium salt[l]. The latter sequence is preferable for anilines with ER substituents. Rearrangement and cyclizalion occurs on treatment of the anilinosulfonium salts with EtjN. The initial cyclization product is a 3-(methylthio)indole and these can be desulfurized with Raney nickel. Use of 2-(methylthio)acetaldehyde generates 2,3-unsubstituled indoles after desulfurization[2]. Treatment of 3-methylthioindoles with tri-fiuoroacetic acid/thiosalieylie acid is a possible alternative to Raney nickel for desulfurization[3]. 

An interesting class of 2-imino-3-amino-4-thiazolines (408) has been described (578, 701, 726). These 3-amino derivatives of 4-thiazoiine may also be prepared from 2,3-diaminothiazolium salts (406) in basic medium (101) or through the acid-catalyzed rearrangement of 2-acylaminoimino-3-phenyl-4-phenyl-4-thiazolines (407) (Scheme 233) (99, 724). 

Mercapto-imida2oliuin inner salts have been reported to rearrange under the influence of hydrochloric acid, producing S-aminothiazolium chlorides (Scheme 25) (36). Their N-acylated derivatives are obtained by cyclization of N-thiobenzoyl alkylaminoacetonitriles, effected with acyl or sulfonyl halides (Scheme 26) (34, 35). 

Ethynyl carbinols rearrange to conjugated unsaturated aldehydes. Copper or silver salts cataly2e isomeri2ation of the acetate to an aHenic acetate, which can be hydroly2ed to an unsaturated aldehyde (204). 

Most other acylating agents act on salts of either primary or secondary nitroparaffins by O-acylation, giving first the nitronic anhydrides which rearrange to give, eg, nitrosoacyloxy compounds (28). 

With sodium azide, salts of secondary nitroparaffins rearrange to N-substituted amides (29). With SO2, primary or secondary nitroparaffins give imidodisulfonic acid salts (30). Potassium nitroform reacts quantitatively with nitryl chloride in ether to form tetranitromethane (31). 

One of the most useful reactions in forming a P—C bond is the Michaehs-Arbusov reaction, which is a characteristic reaction of tricoordinate phosphoms compounds containing an alkoxy group (22). Alkylation of the electron pair is followed by rearrangement of the initial phosphonium salt. 

Phosphoms haUdes and metals or metal salts form addition complexes. Some typical compounds are PCl iSbCl and PCl iAlCl. The trivalent complexes contain metal—phosphoms bonds. The pentavalent complexes involve rearrangements to produce assembles of tetrahedral PX cations and various anions. 

Henkel Rearrangement of Benzoic Acid and Phthalic Anhydride. Henkel technology is based on the conversion of benzenecarboxyhc acids to their potassium salts. The salts are rearranged in the presence of carbon dioxide and a catalyst such as cadmium or zinc oxide to form dipotassium terephthalate, which is converted to terephthahc acid (59—61). Henkel technology is obsolete and is no longer practiced, but it was once commercialized by Teijin Hercules Chemical Co. and Kawasaki Kasei Chemicals Ltd. Both processes foUowed a route starting with oxidation of napthalene to phthahc anhydride. In the Teijin process, the phthaHc anhydride was converted sequentially to monopotassium and then dipotassium o-phthalate by aqueous recycle of monopotassium and dipotassium terephthalate (62). The dipotassium o-phthalate was recovered and isomerized in carbon dioxide at a pressure of 1000—5000 kPa ( 10 50 atm) and at 350—450°C. The product dipotassium terephthalate was dissolved in water and recycled as noted above. Production of monopotassium o-phthalate released terephthahc acid, which was filtered, dried, and stored (63,64). 

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