Ketones synthesis from lactones

The addition of Grignard reagents to aldehydes, ketones, and esters is the basis for the synthesis of a wide variety of alcohols, and several examples are given in Scheme 7.3. Primary alcohols can be made from formaldehyde (Entry 1) or, with addition of two carbons, from ethylene oxide (Entry 2). Secondary alcohols are obtained from aldehydes (Entries 3 to 6) or formate esters (Entry 7). Tertiary alcohols can be made from esters (Entries 8 and 9) or ketones (Entry 10). Lactones give diols (Entry 11). Aldehydes can be prepared from trialkyl orthoformate esters (Entries 12 and 13). Ketones can be made from nitriles (Entries 14 and 15), pyridine-2-thiol esters (Entry 16), N-methoxy-A-methyl carboxamides (Entries 17 and 18), or anhydrides (Entry 19). Carboxylic acids are available by reaction with C02 (Entries 20 to 22). Amines can be prepared from imines (Entry 23). Two-step procedures that involve formation and dehydration of alcohols provide routes to certain alkenes (Entries 24 and 25). 

A brief review of procedures for asymmetric metal-catalyzed Baeyer-Villiger oxidations is given with asymmetric copper-catalyzed synthesis of 3-phenyl-2-oxepanone as representative of the enantioselective synthesis of lactones from cyclic ketones . 

Inanaga showed that the presence of HMPA also accelerates the Barbier addition of alkyl halides to ketones and significantly improves the yield of the adducts.14 He also found that HMPA was a useful additive in the Sml2-mediated synthesis of lactones from bromo esters and ketones (Scheme 2.5). Since Inanaga s pioneering work, the Barbier reaction employing Sml2 HMPA... 

Lactones, formation as side reaction in peptide synthesis 81S333. Lactones, formation from bridged bicyclic ketones 81T2697. 

Vandewalle et al. have also used oxidative ring opening of one side of a norbomanone to prepare a number of iridoids, culminating in a synthesis and correction of the structure of specionin. At first they described the synthesis of teucrium lactone (425) and a loganin precursor (472) from the Diels-Alder adduct 473 of cyclopentadiene and methyl ( )-crotonate (Scheme 44). The same paper describes the preparation of the all-enafo-isomer 474 of ketone 475, from... 

Perhaps the only true homoenolates used in synthesis are derived by metallation of derivatives of 3-haloacids. The acids themselves 12 give lithium 3-halocarboxylates 13 and hence by metallation the homoenolate which probably exists as 15, an analogue of the dilithium enolates of carboxylic acids (chapter 2). Reaction 16 with aldehydes or ketones gives y-lactones 19, by a homoaldol reaction via y-hydroxyacids 18, common products from addition of acid homoenolates to carbonyl compounds.3... 

An interesting route to a-carboxy-8-lactones (81) and a-methylenelactones (80), based on hydrolysis of Knoevenagel products (79) of Meldrum s acid with cyclic aliphatic ketones (78), has been developed (Scheme 14). Reduction of 5-methylene derivatives of Meldrum s acid has been performed catalyti-caiiyi30 or by use of LAH. Imidoylation reaction of Meldrum s acid and subsequent solvolysis of the resulting (82) yields -enamino esters (83) in good yields.Flash vacuum pyrolysis of alkylidene derivatives of Meldrum s acid can be used to prepare methylene ketenes (84), a class of compounds difficult to prepare by conventional methods. By this procedure, methylene ketenes are obtained from aromatic aldehydes and ketones and from aliphatic ketones in only two steps. Intramolecular trapping of the methylene ketene obtained from the ketone (85) has been used successfully in the synthesis of the naphthol (86). ... 

As mentioned in Sect. 2.3, Inanaga and co-workers have demonstrated that Barbier-type reactions of organic halides with carbonyl compounds are promoted by addition of HMPA [16]. They reported a mild convenient method for the direct synthesis of lactones from bromo esters and ketones or aldehydes by using a HMPA-promoted Barbier-type reaction with Sml2 (Scheme 13). They also found that the SmI2/THF-HMPA system was highly useful for the generation of... 

Ketone synthesis. 5-Keto-a-amino acid derivatives and 2-oxathianyl ketones are accessible from the functionalized organocoppers and relatively simple acid chlorides. Thioesters can be used instead of acid chlorides for ketone synthesis. Addition to the carbonyl group. Reaction at the aldehyde function of jS-formyl esters is under chelation control. The entering group becomes trans to the original chain in the y-lactones thus generated. More readily understood is the diastereoselec-tivity in the reactions of protected a-amino aldehydes. ... 

In these oxidations the use of hydrated CUSO4 is mandatory. In fact, it was found that addition of catalytic amounts of water to the solid oxidant creates a more reactive oxidant for the synthesis of lactones from hydroxyaldehydes (eq lO). Small quantities of aqueous t-butanol added to the solid oxidant permit the direct conversion of alkenes to a-hydroxy ketones anda-cUketones (eq 11). Normally, alkenes are inert to the solid oxidant. These differences are attributed to the formation of a thin aqueous... 

Oxone in conjunction with OSO4 cleaves alkenes to ketones or carboxylic acids (eq 43). This protocol has the advantage over traditional methods in that there is no need for intermediate 1,2-diols. This method has been exploited in the direct synthesis of lactones from alkenols (eq 44) and tetrahydrofuran-diols from 1,4-dienes as well. ... 

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