Deoxybenzoin

Figure Bl.16.10. Intensity of CFI2 resonance as a function of delay time in A dibenzyl, B deoxybenzoin, and C deoxybenzoin in presence of thiol scavenger. Reprinted from [25].

Recently, Koitai et al. (17) have shown that 5,5-diphenyl-2,4-thiazolidinedithione (15) with aluminum chloride in refluxing toluene gives 4,5-diphenyl-A-4-thia2oline-2-thione (16) (Scheme 7). 3-Methyl-4,5-diphenyl (17) and 4,5-diphenyl-A-4-thia2oline-2-thiones (16) are obtained in very low yields (1 to 5%) as by-products of the reaction between deoxybenzoin. benzoin. l,2-diphenyl-1.2-ethanediol. 1.2-diphenylethanol, or benzil, and Sg in hexamethylphosphoamide (18), The transformation of A-4-thiazoline-2-ones to the corresponding thiones by P2S5 (19) is of little synthetic value since the latter are more easily prepared. 

Some trivial names are retained acetone (2-propanone), biacetyl (2,3-butanedione), propiophen-one (CgHj—CO—CH2CH3), chalcone (C(,H5—CH=CH—CO—CgH5), and deoxybenzoin (C<,H5—CH3—CO—C H ). 

The synthesis of deoxybenzoin from phenacetyl chloride and benzene by the Friedel-Crafts reaction has been described. For symmetrically substituted deoxybenzoins, direct reduction of the readily accessible benzoin is a more convenient method. Reduction of benzoin by zinc dust and acetic acid, and by hydrochloric acid and granulated tin or amalgamated powdered tin has been reported. The present method is based on a publication of the authors. ... 

Delepine reaction, to prepare 2-bromo-allylamine, 43, 6 Deoxyanisoin, 40,16 Deoxybenzoin, 40,17 Deoxypiperoin, 40,17 Desylamine, 41, 87... 

Oxidation of chalcones with TTN has been studied in detail (95, 96), and it has been shown that the products obtained depend on the amount of reagent and the solvent employed. Oxidation with 1 equivalent of TTN in methanol, methanol-chloroform, or methanol-boron trifluoride leads to acetals of the type (XXXIV) (see also Scheme 21) in yields of 20-80%. When 3 equivalents of TTN are employed, however, and aqueous glyme containing a little perchloric acid used as solvent, the products are benzils. This remarkable transformation, which proceeds in yields varying from moderate to good (40-80%), involves three distinct oxidations by TTN, and these are outlined in Scheme 22. Each individual step in this reaction sequence has been investigated in detail, with the result that useful procedures have been developed for the oxidation of both deoxybenzoins and benzoins to benzils with TTN (96). 

These conclusions were supported by the results obtained in a study of the reactions of various types of acetylenes with TTN (94). Hydration of the C=C bond was found to occur to a very minor extent, if at all, with almost all of the compounds studied, and the nature of the products formed was dependent on the structure of the acetylene and the solvent employed. Oxidation of diarylacetylenes with two equivalents of TTN in either aqueous acidic glyme or methanol as solvent resulted in smooth high yield conversion into the corresponding benzils (Scheme 23). The mechanism of this oxidation in aqueous medium most probably involves oxythallation of the acetylene, ketonization of the initially formed adduct (XXXV) to give the monoalkylthallium(III) derivative (XXXVI), and conversion of this intermediate into a benzoin (XXXVII) by a Type 1 process. Oxidation of (XXXVII) to the benzil (XXXVIII) by the second equivalent of reagent would then proceed in exactly the same manner as described for the oxidation of chalcones, deoxybenzoins, and benzoins to benzils by TTN. The mechanism of oxidation in methanol solution is somewhat more complex and has not yet been fully elucidated. 

Highly arylated ketones have been prepared successfully. For example, arylation of the enolate of the deoxybenzoin 4 gives 1,1,2-triarylethanones that are related to substances such as tamoxifen.176... 

The synthesis of isoxazoles by use of azolides is illustrated by the following example of 3,4-diphenyl-5-methylisoxazoles, prepared by conversion of the deoxybenzoin oximes with JV-acetylimidazole with the aid of butyllithium 1381... 

In contrast to the oxidation of prochiral esters and amides, which induces only moderate ee, sodium enolates of ketones give high stereoselectivity with (+)-147 or (—)-147 as the oxidant (Scheme 4-56 and Table 4-21). The highest stereoselectivity has been observed in the oxidation of the sodium enolate of deoxybenzoin 150, in which benzoin 149 can be obtained in over 95% optical purity. 

The Williamson alkylation of benzoin and deoxybenzoin, using procedure 3.1.1.B, produces dialkoxystilbenes and alkoxystilbenes (>90%), respectively, together with lesser amounts of C,0-dialkylated and C-alkylated derivatives [18]. The yields are... 

If hydrogen sulfide is introduced for 4 hours into a solution of 0.2 mol of an a-diketone in methanol and 0.02 mol of pyridine, a monoketone is obtained. The yield of deoxybenzoin from benzoin is quantitative. 

The isopavine bases, ( )-amurensinine (25) (81,135), ( )-0-meth-ylthalisopavine (26) (136), ( )-reframidine (27) (77), and ( )-reffamine (28) (77) were synthesized by the above-mentioned classical route, where deoxy-benzoins were utilized as starting materials. In some cases, some modification to the method has been introduced, particularly involving the formation of the requisite benzylaminoacetals (77,110). The synthesis of ( )-thalisopavine (30) was undertaken along parallel lines to confirm the structure of the naturally occurring base (53). Moreover, both ( )-reframoline (29) and its positional isomer ( )- 146 were synthesized in an attempt to establish the position of the phenolic hydroxyl (110). The synthesis of ( )-reframine (28) from the properly substituted deoxybenzoin 94 has been outlined in Scheme 16 as a typical example (77). 

Carbanions derived from substances containing active methylene groups are known to react with acetylenic esters leading to heterocyclic compounds. Deoxybenzoins, for example, react with phenylpropiolates... 

Sanduja, R. Weinheimer, A.J. Alam, M. (1985) Albizoin isolation and structure of a deoxybenzoin from the marin mollusk Werito albicilla. J. Chem. Res. (S), 56-7. 

A patent (67MIP21000) has described a general method for the preparation of 2,3-disubstituted quinolizinium ions (149 Scheme 88), a method closely related to the Westphal synthesis viz. [4 + 2] cyclizations). In the example given, 2-picolinaldehyde is allowed to react with deoxybenzoin and the resulting aldol acetylated and quaternized with phenacyl bromide to yield a salt which can be cyclized and cleaved by action of dibutylamine to afford 2,3-diphenylquinolizinium bromide (149) in 68-74% yield. It is claimed that quaternary salts analogous to (148), but formed by reaction of XCH2R (R = alkoxycarbonyl or cyano, X = halogen) may be used likewise. 

The Friedlander condensation of 2,6-diaminopyridine-3,5-dicarbaldehyde (393) with various ketones has been reported (77JOC3410). Reaction of the aldehyde with acetophenone, with deoxybenzoin and with a-tetralone generates the 5,10-dihydro-l,9,10-anthyridine derivatives (394 R = H), (394 R = Ph) and (395) respectively, whilst with acenaphthenone the nonacyclic anthyridine (396) is obtained. The condensation between 2-amino-3-ethoxy-carbonyI-l,8-naphthyridine (225) and alkyl carboxylates under basic conditions produces 4-hydroxy-1,9,10-anthyridin-2-ones (397) (79BAP571). 

Hydrazones of benzophenone, deoxybenzoin, acetophenone, 4-te,r(-butylcyclohexanone. cholestan-3-one, and decan-2-one are also converted into CF2 derivatives in about 70% yield when treated with excess iodine monofluoride.,2 124... 

Synthesis. Deoxybenzoin is converted to the corresponding oxime by treatment with hydroxylamine under basic conditions with sodium acetate in aqueous ethanol or in toluene in the presence of potassium hydroxide in absolute ethanol. Treatment of the oxime under nitrogen with two equivalents of butyllithium in tetrahydrofurane is followed by cyclization in ethyl acetate or acetic anhydride to the isoxazoline derivative. Finally, treatment of the isoxazoline with cold chlorosulfonic acid followed by reaction of the intermediate with aqueous ammonia affords the desired product. (Talley, 2000a Sorbera, 2001b). 

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