Metallates with carbonyl compounds

Figure 6.3. Apparatus for the reaction of alkali metals with carbonyl compounds and the separation of the solid adducts. [Adapted from Ref. 9.] A, separatory funnel in which the reaction is carried out B, cylinder with inert atmosphere C, perforated porcelain disc with filter paper D, entry of inert gas (H2 or CO2) from Kipp apparatus E, wash ether reservoir.

Reactions of similar organoalkynyl/allenyl silanes containing various metals with carbonyl compounds to give propargylic products have been reported. " Conjugate addition of allenyl stan-nanes to Q , -unsaturated carbonyl compounds to give propargylic products can be effected in the presence of titanium(IV) chloride. ... 

Reactions of metallated hetarenes with carbonyl compounds and their imino derivatives 99PHC21. 

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 . 

Schollkopf, U., Schroeder, R., and Stafforst, D., Reaction of a-metalated diethyl isocyanomethyl- and a-isocyanobenzylphosphonates with carbonyl compounds, Justus Liebigs Ann. Chem., 44,1974. 

An interesting novel coupling reaction of allenes with carbonyl compounds mediated by a lanthanide metal species was reported recently [80], The samarium(II) iodide-mediated reaction of various ketones or aldehydes 153 with methoxyallene (56) afforded exclusively y-addition products 4-hydroxy-l-enol ethers 154 in moderate to good yields with low cis/trans selectivity (Scheme 14.39). 

As discussed in previous sections, high-valent carbene complexes of early transition metals have ylide-like, nucleophilic character. Some Schrock-type carbene complexes react with carbonyl compounds in the same manner as do phosphorus ylides, namely by converting the carbonyl group into an alkene. 

Metalations with organolithium compounds, 8, 6 26, 1 27, 1 Methylenation of carbonyl groups, 43, 1 Methylenecyclopropane, in cycloaddition reactions, 61, 1... 

Various nitro compounds have been condensed with carbonyl compounds in reactions catalyzed by alkaline earth metal oxides and hydroxides 145). It was found that the reactivities of the nitro compounds were in the order nitro-ethane > nitromethane > 2-nitropropane, and those of carbonyl compounds were propionaldehyde > isobutyraldehyde > pivalaldehyde > acetone > benzaldehyde > methyl propionate. Among the catalysts examined, MgO, CaO, Ba(OH)2, and Sr(OH)2, exhibited high activity for nitroaldol reaction of nitromethane with propionaldehyde. In reactions with these catalysts, the yields were between 60% (for MgO) and 26% (for Sr(OH)2) at 313 K after 1 h in a batch reactor. On Mg(OH)2, Ca(OH)2, and BaO, the yields were in the range of 3.8% (for BaO) and 17.5% (for Mg(OH)2). Investigation of the influence of the pre-treatment... 

Less success has been obtained with removable N-substituents, however, the trityl and THP derivatives of 4-bromopyrazole both giving low yields of products derived from reaction of the lithio derivatives with carbonyl compounds [62CB222 82ACS(B)101]. Magnesium metal has also been used to produce l-methyl-4-(trimethylsilyl)pyrazole by an in situ Grignard reaction on the analogous 4-bromo compound in HMPT (84JOC4687). 

A number of low-valent or zero-valent metals are able to promote Reformatsky-type reactions of a-bromoesters with carbonyl compounds and related electrophiles60. Starting with calcium and moving rightward along the fourth row of the periodic table, the following metal species have been reported to promote Reformatsky-type reactions ... 

They proposed a polymerization scheme closely related to other well-known chemical reactions of metal alkoxide with carbonyl compounds (20). In Scheme 2, complex [A] is converted to [B] by hydride ion transfer from the alkoxyl group to the carbon atom of aldehyde (Meerwein-Ponndorf reduction). Addition of one molecule of monomer to the growing chain requires transfer of the alkoxide anion to the carbonyl group to form a new alkoxide [C]. Repetition of these two consecutive processes, i.e., coordination of aldehyde and transfer of the alkoxide anion, constitutes the chain propagation step. 

A variety of macrocyclic complexes which have adjacent nitrogen atoms (cyclic hydrazines, hydrazones or diazines) are formed by condensations of hydrazine, substituted hydrazines or hydrazones with carbonyl compounds. The reactions parallel in diversity those of amines, but are often more facile since the reacting NH2 groups is generally not coordinated and the electrophile is thus not in competition with the metal ion. The resulting macrocycles may be capable of coordination isomerism, since either of the adjacent nitrogen atoms can act as donor atom. 

Reaction XLIII. (c) Condensation of a-Halogen Fatty Acid Esters with Aldehydes and Ketones by means of Zinc or Magnesium (Reformatsky-Grignard). (C., (1901), I., 1196 II., 30 (1902), I., 856.)—This is an extension of the Grignard and zinc alkyl reactions which enables a-halogen esters to be condensed with carbonyl compounds as if they were simple alkyl halogen compounds. The zinc or magnesium alkyl derivative is neither prepared beforehand nor isolated in the reaction, but there is little doubt that some such compound is transitorily formed. Zinc is the metal... 

Thiols, like alcohols, react readily with carbonyl compounds. The resulting hemithioacetals (102), thioacetals (103) and their cyclic analogues (104) and (105) are of considerable synthetic importance. These compounds are more stable to acid hydrolysis than their oxygen analogues but can be hydrolyzed under mild conditions in the presence of metal ions such as Ag(I) (equation 29). The synthetic importance of the metal ion-promoted hydrolyses has led to the publication... 

Application of the alcohol interchange reaction (method 6) is limited by certain phenols and also di and trisubstituted glyoxides (while the reaction of metals with glycols gives only monosubstituted derivatives) [745, 621, 575, 1584,1369]. As redox processes (method 7) can be considered the Grignard-type reactions — the interaction of metal alkyls with carbonyl compounds,... 

Homoallylic alcohols. Tn the presence of metallic tin, both allyl iodide and bromide react with carbonyl compounds at room temperature to form homoallylic alcohols in 75 90% yield. Presumably a diallyltin dihalide is formed initially.1 Examples ... 

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