Ketones, condensation with organometallic

As an extension of the reaction of sulphinates with organometallic compounds, the Claisen-type condensation between ketone enolate anions 101 and arenesulphinates may be considered. It was found161,162 that this reaction provides an interesting synthetic approach to a-ketosulphoxides 102 (equation 54 Table 9). 

The Oppenauer oxidation is a common side reaction during the condensation of organometallic compounds with aldehydes and ketones, something that very often comes as a surprise for the unaware chemist. This has been observed in condensations of diverse organometallic species, for example chromium,61 Zr62 and Mg63 organometallics. This side reaction... 

In this reaction organometallic compounds incapable of existence in high concentration are formed and utilized immediately. When an aide hyde or ketone is condensed with a halo ester the product is a fi-bydroxy ester. Sometimes dehydration occurs to give olefinic esters directly (method 19). The use of an ester as the carbonyl compound leads to /3-keto esters (method 234). The halo esters most commonly employed are of three types XCHjCOjCjHj, RCHXC02CjHj, and R CXCO CjH,. Vinylogous halo esters, such as y-bromocrotonate, and certain benzyl halides have been used with variable success. 

Ketones can be prepared starting from esters via the intermediate 2-acylbenzothiazoles (511) which are easily obtained by condensation with 2-lithiobenzothiazole (230). The reaction of these compounds with an organometallic reagent and subsequent quaternization of the heterocyclic ring affords the A -methylbenzothiazolium salts (512) which upon treatment with a base yield the corresponding ketones (Scheme 120) <91BCJ3256>. 

Many examples of the formation of new six-membered rings containing a nitrogen atom in the reaction of isatoic anhydrides with ketones, diketones, various ether derivatives, lactones, and organometallic compounds are known. Thus, the anhydrides 2 and 34 condense with acetophenones and co-methoxyacetophenones in the presence of lithium diisopropylamide at low temperatures with the formation of derivatives of quinolone 35 [17, 18],... 

The presence of unsaturation in the side chain is also compatible with antihistaminic activity. Mannich condensation of p-chloroacetophenone with formaldehyde and pyrollidine affords the amino ketone, 109. Reaction with an organometallic reagent from 2-bromopyridine gives 110. Dehydration leads to triproli-dine (111). ... 

A new approach to a variety of a-branched alkynes 70 was achieved by a Knoevenagel type condensation of 4-unsubstituted isoxazolin-5-ones 66 with aldehydes or ketones 67, followed by conjugate addition of an organometallic species and nitrosative cleavage of the heterocyclic ring <02SL1257>. 

Cp 2La CH(SiMe3)2 reacts with 3-pentanone to form the solvated enolate, Cp 2La —O—C(Et)=CHMe Et2CO (equation 9a), while with acetone it forms a chelate (equation 9b) after intramolecular aldol condensation. The reaction of the precursor bistrimethylsi-lyhnethyl organometallic with hydroxyketone, preformed from the pentanone, yields the enolate ketone solvate. This difference between acetone and 3-pentanone presumably reflects the difference in strain in the condensation product because the ethyl groups in 3-pentanone are rather much bigger than the methyl groups in acetone. 

Several other preparative methods, involving the condensation of (i) N-(trimethylsUyl)phosphinimines and carbonyl compounds and (ii) organometallic reagents with nitriles followed by quenching with chlorotrimethylsilane, have been used for the preparation of other aldehyde- and ketone-derived... 

One of the most effective ways of preparing enantiomerically pure secondary amines is the addition of organometallic reagents to chiral sul fmimines, which are prepared by the condensation of an aldehyde (or ketone) with a sulfinamide. The preparation of /-butyl sulfinamide had been problematic, but the synthesis (and supplies) now seems to be more reliable. 

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