Deoxybenzoin, from benzoin

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 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). 

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). 

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. 

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