From deoxybenzoine

The same one-carbon unit has been employed in a convenient isoflavone synthesis from deoxybenzoins (76S326). Other methods of ring closure of phenyl benzyl ketones to this heterocycle have been reviewed (B-62MI22400) and include triethyl orthoformate (56PIA(A)(44)36), zinc cyanide (58CB2858), ethyl formate (80BCJ831) and ethoxalyl chloride (70JCS(C)1219). 

Referring to the initial formation of imidoyl compounds in the course of the acid-catalyzed ketone-nitrile reaction95,96,98 Garcia and coworkers97 described a new one-pot synthesis of 1-substituted 3-arylisoquinolines 149 from deoxybenzoins 148 and nitriles (equation 49). The authors used two procedures applying either phosphorus oxychloride at reflux or phosphorus pentoxide at room temperature. 

The conversion of active-methylene compounds into 2-alkylidene derivatives of 1,3-dithiolans by base-catalysed condensation with carbon disulphide followed by treatment with 1,2-dihalogenoalkanes has been further exemplified, and extended to the synthesis of substituted alkyl-idene derivatives of 1,3-diselenolans and 1,3-diselenans. With dimethyl malonate, carbon diselenide, and either 1,2-dibromoethane or 1,3-dibromo-propane, for example, the compounds (142) and (143), respectively, were formed. Analogously, the dithiolate anion obtained from 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].

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. ... 

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). 

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. 

The same sequence of reactions from o-hydroxylated deoxybenzoins (250) forms 3-benzylbenzofurans, e.g., 251.584 Similarly, o-hydroxylated benzils with suitable a-bromoalkanoic esters give 3-benzoylbenzo-furans397,585 (e.g., 253, R = H).586 When R = OMe, the resulting... 

The Michael addition of deoxybenzoin to several ethyl a-acetylcinnamates, obtained from ethyl acetoacetate and an aromatic aldehyde in the presence of piperidine, resulted in the formation of 1,5-diketones. Cyclization to 4/f-pyrans occurred in acetic acid and p-toluenesulfonic acid (76DC(B)739). 

The formation of pyran-2-ones from ethyl 3-phenylpropynoate and some deoxybenzoins has been studied in some detail (66JOC2167). Attempts to isolate the initial Michael addition... 

The photochemistry of benzaldehyde (90% 13C=0), 519, deoxybenzoin (99%) 13C=0), 521, and / -chloro benzoin (99% 13C=0), 522, in cyclohexane-Dn solution has been studied633 by spectroscopic techniques, such as XH chemically induced dynamic nuclear634 or electron polarization635 (CIDNP/CIDEP) or dynamic nuclear polarization636 (DNP). In all these cases the formation of benzaldehyde-D with emissive 13C=0 polarization has been observed and the results rationalized by intermolecular hydrogen (deuterium) abstraction by the photoexcited ketones from the solvent molecules and by reactions of cage-escaped radicals (equations 303-308), Benzoin, 520, is formed also. 

It has been documented that the photoexcited deoxybenzoin can abstract H as well as D from appropriate solvents. Hydrogen abstraction by triplet 521 from cyclohexane-Hi2 (rate constant 2.1 x 105 mol-1 s 1) is faster than w-cleavage whereas deuterium abstraction (3.9 x 104 mol-1 s 1) is competitive with a-cleavage (deuterium isotope effect of 5). 

As seen in the gitonic and vicinal systems, ammonium and related cationic centers may be components of superelectrophiles and reactive dications having the 1,3-dicationic structure. Several types of superelectrophilic aza-carbo dications have been studied in which protonated nitro groups are involved. For example, it was found that nitroethylene reacts with benzene in the presence of 10 equivalents of CF3SO3H to give deoxybenzoin oxime in 96% yield (eq 58).71 Since the reaction does not occur with only one equivalent of CF3SO3H, the formation of the /V./V -dihydroxy iminium-methyl dication 197 was proposed. In spectroscopic studies, the stable dication (199) can be directly observed by H and 13C NMR spectroscopy from solutions of l-nitro-2-methyl-l-propene (198) in CF3SO3H (eq 59). 

From benzylcyanide and deoxybenzoin alkyl derivatives can be formed by tho action of sodium and alkyl halides ... 

Polymer-supported diacetoxyiodobenzene can be used advantageously in the synthesis of isoflavones from 2-hydroxychalcones <02S2490>. Treatment of deoxybenzoins with CS2 and an alkyl halide under phase transfer conditions leads to 2-(alkylthio)isoflavones <02TL6113>. 

On successive treatment with trimethyloxonium tetrafluoroborate, triethylamine and aqueous acid, oxime acetate 83 prepared from cyclohexanone oxime and Ac20 yields a-acetoxy ketone 87 (Scheme 7). A similar result is obtained with other symmetric ketones including 4-heptanone, deoxybenzoin and dibenzyl ketone. 87 can also be formed by the reaction of cyclohexanone and O-acetyl-Af-methylhydroxylamine hydrochloride upon hydrolysis. If the reaction time is prolonged prior to hydrolysis, ketoamide 89 is isolated as the main product. The key step of the reaction is the [l,3]-acetoxy shift of 7V-acetoxyenamine 85 to the a-acetoxyimine 86. The formation of 89 provides support for the intermediacy of acetoxyimine 86 in the reaction sequence. The evidence available suggests that the [l,3]-acetoxy migration proceeds via a Claisen-type rearrangement (Scheme 7)78. 

The reaction has been adequately discussed by Pozharskii.3 Recently, 1,2,4,5-tetraarylimidazoles and 1,2,3,4,5-pentaarylimidazo-lium salts have been prepared78 from [N-(a-chloroaryliden)anilino]-deoxybenzoin chlorides (10) with ammonia or an aromatic primary amine, followed in the latter case by reaction with thionyl chloride. 

Recent work on the thermal indolization of arylhydrazones has introduced new synthetic possibilities for azaindoles. Kelly et al. refluxed cyclohexanone and deoxybenzoin 2-pyridylhydrazones in diethylene glycol to give 5,6,7,8-tetrahydro-a-carboline (42, R = H) and 2,3-diphenyl-7-azaindole in 70 and 56% yields, respectively, compared with 53 and 12% reported earlier. Similarly, y-carboline 29 was obtained in 95 % yield from cyclohexanone 4-pyTidylhydrazone (lit. 48% ). Several 7-azaindole derivatives were prepared in the same manner. The yields ranged from 5 % for azaindolenine (31) to 88% for 3-phenyl-7-azaindole. 3,3-Dimethyl-7-azaindolenine was obtained in 47 % yield from the isobutyralaldehyde hydrazone. The novel cyclic compounds 40 and 41 were obtained from the 2-pyridylhydrazones of cyclopentanone, a-indanone, and a-tetralone in 67, 95, and 77% yields, respectively. Unfortunately, all attempts to cyclize the acetone, pyruvic acid, and ethyl pyruvate hydrazones were unsuccessful. Also, cyclohexanone and methyl ethyl ketone 5-nitro-2-... 

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