Carbonyl compounds reaction with benzylic

Hamogemeoms catalytic transfer-iyilrogeiiathH. Sa.metal catalyst for transfer of hydrogen from primary alcohols to a,p-unsaturated carbonyl compounds. Thus when benzyl alcohol is heated under nitrogen at 200° for 2 hr. with benzalacetone and the catalyst, benzaldehyde (90% yield) and 4-phenylbutane-2-one (92% yield) are formed. The reaction can be carried out in a... 

The mechanisms of reactions of benzylmagnesium halides can be either homolytic or concerted. As with allylic Grignard reagents, also reversible addition reactions with benzylic Grignard reagents and carbonyl compounds have been reported. In general, yields of normal alcohols are low, and such alcohols are obtained in much better yields by use of dibenzylcadmium [66] or benzyllithium [67]. However, in 1980, it was demonstrated that, by far, the best and quickest results for the synthesis of these normal addition reaction products are obtained by applying benzylic halides in the one-step Li-Barbier reaction under ultrasonic irradiation [68,69]. 

Quaternary ammonium salts derived from ephedrine have been used as catalysts for the addition of dialkylzinc to carbonyl compounds (Section D.1.3.1.4.) and are useful as phase-transfer catalysts for alkylation of carbonyl compounds17 and reductions18. N-Benzyl-A -methylephedri-nium salts 10 have found varied application they are easily prepared from A -methylephedrine 913 by reaction with benzyl halide in toluene1 or chloroform/methanol (1 1)18 in high yield. Ref 18 also gives the preparation of other ephedrinium and pseudoephedrinium salts. 

The oxidations of benzyl alcohols and substituted mandelic acids by pyridinium chlorochromate have been described. This oxidant is a complex of Cr03,pyridine and hydrochloric acid, and is known to convert alcohols into carbonyl compounds in high yield. In the reaction with benzyl alcohol the reaction is... 

Alkylation and Substituted Alkylation—Reactions in this group (other than hydroxyalkylations and benzylations effected by carbonyl compounds, dealt with below) are not numerous. Mannich aminomethylations have been carried out with 2- and 4-picoline and 2-ethylpyridine, formaldehyde and a number of amines , but yields are poor . 

It is important to note that the one-step conversion of 27 to 28 (Scheme 4) not only facilitates purification, but also allows differentiation of the two carbonyl groups. After hydrogenolysis of the iV-benzyl group (see 28—>29), solvolysis of the -lactone-ring in 29 with benzyl alcohol and a catalytic amount of acetic acid at 70 °C provides a 3 1 equilibrium mixture of acyclic ester 30 and starting lactone 29. Compound 30 can be obtained in pure form simply by washing the solid mixture with isopropanol the material in the filtrate can be resubjected to the solvolysis reaction. 

Durst and coworkers were the first to report the condensation of chiral a-sulphinyl carbanions with carbonyl compounds . They found that metallation of (+ )-(S)-benzyl methyl sulphoxide 397 followed by quenching with acetone gives a mixture of dia-stereoisomeric S-hydroxy sulphoxides 398 in a 15 1 ratio (equation 233). The synthesis of optically active oxiranes was based on this reaction (equation 234). In this context, it is interesting to point out that condensation of benzyl phenyl sulphoxide with benzaldehyde gave a mixture of four j8-sulphinyl alcohols (40% overall yield), the ratio of which after immediate work-up was 41 19 8 32 . 

The development of the Grignard-type addition to carbonyl compounds mediated by transition metals would be of interest as the compatibility with a variety of functionality would be expected under the reaction conditions employed. One example has been reported on the addition of allyl halides to aldehydes in the presence of cobalt or nickel metal however, yields were low (up to 22%). Benzylic nickel halides prepared in situ by the oxidative addition of benzyl halides to metallic nickel were found to add to benzil and give the corresponding 3-hydroxyketones in high yields(46). The reaction appears to be quite general and will tolerate a wide range of functionality. 

Preparation of (l-aminopropyl)phenylphosphinic acid — Reaction of a carbonyl compound with benzyl carbamate and a dichlorophosphine... 

In contrast to the Michaelis-Arbuzov reaction, triaryl phosphites prove to be quite useful for addition to a,(3-unsaturated carbonyl compounds in this type of reaction. A wide variety of unsaturated compounds have been utilized successfully as substrates for such additions, including condensation products of the simple carbonyl compounds with urea,229 thiourea,230-233 N-substituted thioureas,232 234 235 ethyl carbamate,236 2-imidazolidinone,237 2-imidazoli-dinethione,237 and benzyl carbamate.238-240... 

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