Benzylidene-acetone Preparation

On account of its exceptionally penetrating nature, benzylidene acetone should be used in perfumery with great caution, and only as a 10% solution in alcohol. Its stability to alkali makes it of special value for soap-perfume oils. In its concentrated state benzylidene acetone violently attacks the skin. 

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C10H12O, Mr 148.20, pioi.3kPa 233-234°C, df- 0.9849, Up 1.5110, has been identified as a volatile component of cocoa. Benzylacetone is a sweet-flowery smelling liquid, which can be prepared by selective hydrogenation of benzylidene acetone (from benzaldehyde and acetone). It is used in soap perfumes. 

This compound is also of the coumarin family. The fonnula is 3-(alpha-acetonylbenzyl)-4-hydroxycoumarin. In addition to use in anticoagulant therapy in medicine, the compound also has been used as a major ingredient in rodenhcides, where the objective is to induce bleeding and, when used in heavy doses, is thus lethal. The compound can be prepared by the condensation of benzylidene-acetone and 4-hydroxycoumann. 

Preparation of Cinnamic Acid from Benzylidene Acetone... 

In this example, the catalyst was prepared in situ from (dba)2Pd, CHC13 (dba = diphenyl-benzylidene acetone) and triphenylphosphane. The single product results from axial attack of the TMM unit onto the ketone. 

Methyl 4,6-0-benzylidene-3-deoxy-a-D-ribo-hexopyranoside (56) was benzoylated, debenzylidenated, and partially p-toluenesulfon-ylated to 57 this was converted into 58 by reaction with sodium iodide, followed by catalytic reduction. The methanesulfonate of 58 was converted into 59 by reaction with sodium azide in N,N-dimethylformamide, and 59 was converted into 4-azido-3,4,6-trideoxy-a-D-xylo-hexose (60) by acetolysis followed by alkaline hydrolysis. Reduction of 60 with borohydride in methanol afforded 61, which was converted into 62 by successive condensation with acetone, meth-anesulfonylation, and azide exchange. The 4,5-diazido-3,4,5,6-tetra-deoxy-l,2-0-isopropylidene-L-ara/uno-hexitol (62) was reduced with hydrogen in the presence of Raney nickel, the resultant diamine was treated with phosgene in the presence of sodium carbonate, and the product was hydrolyzed under acidic conditions to give 63. The overall yield of 63 from 56 was 4%. The next three reactions (with sodium periodate, the Wittig reaction, and catalytic reduction) were performed without characterization of the intermediate products, and gave (+)-dethiobiotin methyl ester indistinguishable from an authentic sample thereof prepared from (+)-biotin methyl ester. 

When 2-amino-5-chloro-3-methoxycarbonylpyrazine was refluxed with aniline and concentrated hydrochloric acid in acetone for 16 hours, the anil, 5-anilino-2-isopropylideneamino-3-methoxycarbonylpyrazine (22) was formed (432, 778, 780), and 2-amino-5-chloro-3-methoxycarbonyl-6-(l -methylhydrazino)pyrazine with benzaldehyde in ethanol gave 2-amino-6-(2 -benzylidene-r-methylhydrazino)-5-chloro-3-methylcarbonylpyrazine (23) (809). A series of hydrazones has been prepared by refluxing equimolar quantities of 2-hydrazinopyrazine and carbonyl compounds in the presence of catalytic quantities of p-toluenesulfonic acid in benzene (1195). Other preparations of similar hydrazones have been described (1196). 

Synthesis of D liicuronolactone.—n-Glucuronolactone may be prepared from gum arabic or by the biological methods of Quick/ or Williams. A synthetic method, which is however somewhat cumbersome, is that of Zervas and Sessler which involves the oxidation of 1,2-isopropylidene-3,5-benzylidene-D-glucose with alkaline permanganate and subsequent removal of the acetone and benzylidene groups by acid hydrolysis. A simpler synthetic method has been provided by the reviewers and it appears to be of particular value inasmuch as it is a general one. 

Dihydro-2/7-l,3-oxazines (188) are available through a one-pot procedure in which acetyl-acetone is reacted with arylaldehydes and ammonium acetate (Equation (11)) <92JCS(P1)2055>. Assuming that a benzylidene derivative is formed in situ and this reacts with an arylimine, this preparation is included here as a [4 -t- 2]-type. 

The reaction of epoxides of carbohydrates with methylmagnesium iodide gives mainly deoxyiodo alcohols which, on p-toluenesulfonylation, afford derivatives []for example, methyl 4,6-0-benzylidene-3-deoxy-3-iodo-2-0-p-tolylsulfonyl-a-D-glucoside (74), prepared from methyl 2,3-anhydro-4,6-0-benzylidene-at-D-allopyranoside ] which imdergo ready elimination when treated with sodium iodide in acetone (Route A). The general applicability of this route to unsaturated compounds has been noted, and, in the pentose series, it has been applied to the preparation of methyl 4-0-benzyl-2,3-dideoxy- 3-L-glj/cero-pent-2-enoside (79). Here, the elimination occurs much... 

Optimum conditions for the electro-oxidation of l,2 5,6-di-Q-isopropylidene-a-D-glucofuranose to the corresponding 3-uIose have been developed In a study of the hydration of methyl 4,6-0-benzylidene-2-bromo- and 2-chloro-2-deo) -a- and -D-xvlo-hexopvranosid-3-ulose in acetone solution, only the fl-D-xylo-derivatives were observed to hydrate and in another investigation the isomeric composition of freshly prepared D-ribo-hexos-3-ulose in DjO has been examined by H-n.m.r. spectroscopy. Full details have been published on the regioselective monooxidation of unprotected glycosides by reaction of Q-stannyl derivatives with bromine. ... 

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