1.3- Dimethoxy-2-propanone

C f,H2f,0 8545S-25-9) see Retinol (36 -frans)-3-(2,5-dimethoxy-3,4,6-trimethylphenyl)-l-(hexahydro-2-phenyI-l -pyrroIo[l,2-c]imidazoI-3-yl)-l-propanone... 

This extension of the Smith analysis, involving methylation of the polyalcohol, has been studied in detail by Bose, both on model systems and on the Ti fructan.84 When a ffuctan is used, this method may give l-hydroxy-3-methoxy-2-propanone and l,3-dimethoxy-2-propa-none, together with methylated glycerols. These compounds may react further under methanolysis conditions to yield 2,5-dimethoxy-2,5-bis(methoxymethyl)-l,4-dioxane and l,3-dimethoxy-2-propanone dimethyl acetal, respectively. Several of these compounds may be obtained from sucrose by a model reaction. In view of the wide variety of hydroxy compounds obtained in this study,84 their separation and identification as benzeneboronates was investigated, and certain of the latter derivatives were purified by gas-liquid chromatography. The characterization of 1,2- and 1,3-diols by the mass spectra of their cyclic benzeneboronates has also been described.634... 

The optical isomers of DOM have been prepared in two ways. The racemic base has been resolved as the ortho-nitrotartranilic acid salt by recrystallization from EtOH. The (+) acid provides the (+) or S isomer of DOM preferentially. Also, the above-mentioned l-(2,5-dimethoxy-4-methylphenyl)-2-propanone can be reductively aminated with optically active alpha-methyl benzylamine with Raney Nickel. This amine is isolated and purified by recrystallization of the hydrochloride salt. When optically pure, the benzyl group was removed by hydrogenolysis with palladium on carbon. The mp of either of the optical isomers, as the hydrochloride salts, was 204-205 °C. 

Recently, enantioselective hydrogenation has been applied to the reduction of a-oxo acetals. The in situ catalyst [Rh(cod)CI]2/BCPM hydrogenated 1, l-dimethoxy-2-propanone to (/ )-l,l-dimethoxy-2-propanol in 71 % ee and 100% conversion18. 

Dimethoxy-2-pyrrolidinopropene (196) has been shown to be a useful synthon for the synthesis of formylpterins and related compounds. Thus treatment of (196) with nitrosyl chloride, followed by hydrolysis, yields 1,1-dimethoxy-3-oximino-2-propanone (197), which on treatment with amino-malononitrile gives a pyrazine (198) that is suitable for elaboration to a formylpterin (Scheme 89). Two nine-step syntheses, from pyrazine intermediates, of deoxyurothione (199) have been announced. A practical synthesis of the urinary thienopterin urothione (200) still remains a synthetic challenge. ... 

Pyruvic aldehyde dimethyl acetal (1,1 -dimethoxy-2-propanone)... 

Benzophenone p-Chlorobenzophenone 2,2-Dimethoxy-2-phenylacetophenone 1 -Hydroxycyclohexyl phenyl ketone 2-Hydroxy-[4 -(2-hydroxyethoxy) phenyl]-2-methyl propanone... 

A soln. of startg. organocerium compd. (prepared from methylmagnesium bromide and CeCl3) added dropwise to a stirred soln. of a-benzyloxyiminoacetophenone (2S,3S)-l,4-dimethoxy-2,3-butylene acetal in dry THF under N2 at —78°, stirred at — 23° to 0° until t.l.c. indicated completion of reaction (1-3 h), and treated with water - 2S-2-benzyloxyamino-1 -phenyl-1 -propanone (2S,3S)-1,4-dimethoxy-2,3-butylene acetal. Y 84% (99% d.e.). F.e.s. H. Fujioka et al., Chem. Pharm. Bull. 37, 602-5 (1989) from aldoximes with RLi/BF3 cf. K.E. Rodriques et al., Tetrahedron Letters 29, 3455-8 (1988). 

A mixture of 90 g. l,3-dihydroxy-2-propanone, methanol, and Amberlyst 15 cation exchanger stirred 4 hrs. at 100-110° in a pressure vessel l,l-dimethoxy-2-propanone. Y 82%. F. e., also reaction with diols and triols, s. S. K. Gupta, J. Org. Chem. 47, 2642 (1976). 

H NMR (Sadder standard n° 49339M), IR (Sadder standard n° 76412K). l-(2,4-Dimethoxy-3-methylphenyl)-l-propanone... 

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