Ketones 5-7-membered cyclic

Derived from an aldehyde or ketone and an alcohol using an acid catalyst. Ethylene glycol or 1,3-dihydroxypropane are frequently used to give 5-or 6-member cyclic products. 

A standard synthetic sequence for building a six membered cyclic ketone onto an existing aromatic ring is shown in outline as follows Specify the reagents necessary for each step... 

Diols that bear two hydroxyl groups m a 1 2 or 1 3 relationship to each other yield cyclic acetals on reaction with either aldehydes or ketones The five membered cyclic acetals derived from ethylene glycol (12 ethanediol) are the most commonly encoun tered examples Often the position of equilibrium is made more favorable by removing the water formed m the reaction by azeotropic distillation with benzene or toluene... 

Intramolecular acylation of ketones yields cyclic p diketones when the ring that is formed is five or six membered... 

A mechanism of the 1,2-addition of Grignard reagents to ketones has been suggested by Swain involving a six-membered cyclic transition state. Ashby proposed a detailed mechanism as shown in (l)-(2). 

Alkyl sulfonyl chlorides, having an a-hydrogen atom, react with enamines derived from aldehydes and cyclic ketones in the presence of triethylamine to give cyclic sulfones. Thus the enamine (22) gave the four-membered cyclic aminosulfone (143) on reaction with methanesulfonyl chloride (95). 

The aldehyde or ketone, when treated with aluminum triisopropoxide in isopropanol as solvent, reacts via a six-membered cyclic transition state 4. The aluminum center of the Lewis-acidic reagent coordinates to the carbonyl oxygen, enhancing the polar character of the carbonyl group, and thus facilitating the hydride transfer from the isopropyl group to the carbonyl carbon center. The intermediate mixed aluminum alkoxide 5 presumably reacts with the solvent isopropanol to yield the product alcohol 3 and regenerated aluminum triisopropoxide 2 the latter thus acts as a catalyst in the overall process ... 

Ketones Saturated open-chain ketones and six-membered cyclic ketones absorb at 1715 cm-1., five-membered cyclic ketones absorb at 1750 cm J, and ketones next to a double bond or an aromatic ring absorb at 1690 cm-1. 

Having developed effective synthetic methodology for the construction of seven-membered cyclic ethers, we were confident that the problem of the frans-fused bis(oxepane) system could now be addressed on a solid foundation. It was our hope that the breve-toxin-type bis(oxepane) system could be assembled by a stepwise strategy utilizing both photochemical dithioester and reductive hydroxy ketone cyclization methods. 

If 1,4-dihalides are treated with K2pe(CO)4, five-membered cyclic ketones are prepared. ... 

Simple Example Lewis acids, such as AlCl, catalyse the Diels-Alder reaction. Workers used a three-fold excess of butadiene to react with the AlCl complex of 5,6 and 7-membered cyclic enones, e.g, (5), giving excellent yields of eie fused bicyclic ketones (6), Me and H must be cis in (6) as they were aiv in (5). 

No stereoselectivity was observed in the formation of a 1 1 diastereomeric mixture of 2-hydroxy-2-phenylethyl p-tolyl sulfoxide 145 from treatment of (R)-methyl p-tolyl sulfoxide 144 with lithium diethylamide . However, a considerable stereoselectivity was observed in the reaction of this carbanion with unsymmetrical, especially aromatic, ketones The carbanion derived from (R)-144 was found to add to N-benzylideneaniline stereoselectivity, affording only one diastereomer, i.e. (Rs,SJ-( + )-iV-phenyl-2-amino-2-phenyl p-tolyl sulfoxide, which upon treatment with Raney Ni afforded the corresponding optically pure amine . The reaction of the lithio-derivative of (-t-)-(S)-p-tolyl p-tolylthiomethyl sulfoxide 146 with benzaldehyde gave a mixture of 3 out of 4 possible isomers, i.e. (IS, 2S, 3R)-, (IS, 2R, 3R)- and (IS, 2S, 3S)-147 in a ratio of 55 30 15. Methylation of the diastereomeric mixture, reduction of the sulfinyl group and further hydrolysis gave (—)-(R)-2-methoxy-2-phenylacetaldehyde 148 in 70% e.e. This addition is considered to proceed through a six-membered cyclic transition state, formed by chelation with lithium, as shown below . ... 

Photocycloaddition Reactions of Carbonyl Compounds and Alkenes. Photocycloaddition of ketones and aldehydes with alkenes can result in formation of four-membered cyclic ethers (oxetanes), a process often referred to as the Paterno-Buchi reaction.196... 

In order to construct the thiepin conjugation, the seven-membered cyclic ketones containing sulfur could be converted to either their enol ethers or enol acetates. The resulting thiepins should have a number of substituents. The first stable 3,5-diacetoxy-4-phenylbenzo[6]thiepin (15) has been obtained by Hofmann et al. from the diketone (14) by acetylation with acetic anhydride in pyridine in good yield 13). By this methodo-... 

In a related reaction, acyltriphenylgermanes with terminal olefin groups can undergo photocyclization to form five- and six-membered cyclic ketones with an... 

Lastly, the radical inter- and intramolecular cyclizations in the presence of one-electron oxidizing agents as a procedure for the synthesis of five-membered cyclic nitronates can be considered. Radical oxidation of a-nitro ketones (19) in the presence of disubstituted olefins under the action of Mn(OAc)3 was documented (72a) (Scheme 3.22, Eq. 1). 

However, intramolecular O-alkylation can be performed under particular conditions leading to of annelation of a seven-membered heterocycle. Japanese researchers (170) prepared the corresponding seven-membered cyclic nitronates (50a-c) in good yields by the reaction of triethylamine with brominated aryl ketones (49a-c) containing the nitromethyl group in the ortho position. 

New chiral oxazaborolidines that have been prepared from both enantiomers of optically active inexpensive a-pinene have also given quite good results in the asymmetric borane reduction of prochiral ketones.92 Borane and aromatic ketone coordinate to this structurally rigid oxazaborolidine (+)- or (—)-94, forming a six-membered cyclic chair-like transition state (Scheme 6-41). Following the mechanism shown in Scheme 6-37, intramolecular hydride transfer occurs to yield the product with high enantioselectivity. With aliphatic ketones, poor ee is normally obtained (see Table 6-9). 

If the ketone is cyclic, a lactone is the product, but this reaction is practical only with 3-6 membered ring ketones ... 

When 3-chloro-3-phenyl acrylonitrile was involved in this reaction, a bi-cyclic product, 6,6 -diphenyl-4,4 -bis(l,2,3-dithiazine) was formed in good yield [262]. Five-membered cyclic disulfides were obtained in this reaction when ethylenic esters or ketones were taken as an unsaturated substrate (Scheme 61) [263]. 

The two established Hnls, those from L. usitatissimum and P. amygdalus, have found biocatalytic applications for the production of (i )-cyanohydrins. The former of these Hnls is the least widely applied, the natural substrates being acetone cyanohydrin or (i )-2-butanone cyanohydrin (Table 1) [28]. Although an improved procedure for the purification of this enzyme has been reported [27] it is still only available in limited quantities (from 100 g of seedlings approximately 350 U of enzyme are obtained). It was found that this enzyme transforms a range of aliphatic aldehyde and ketone substrates [27], the latter of which included five-membered cyclic (e.g. 2-methylcyclopentanone) and chlorinated ketone substrates. In contrast, attempts to transform substituted cyclohexanones and 3-methylcyclopentanone failed and it was even found that benzaldehyde deactivated the enzyme. 

Reaction of aldehydes and ketones with iminoboranes has been widely investigated. Conditions for the [2 + 2]-cycloaddition between XBNR and R R"CO are relatively good stability of the iminoborane and lack of enolic protons in the oxo compound [Eq. (46)] 14, 19). Relatively less stable iminoboranes, but in some cases the stable ones too, may react with 0X0 compounds by a total opening of the B=N triple bond [Eq. (43)], presumably via a [2 + 2]-cycloaddition [Eq. (42)] (Section V,D). A relatively stable iminoborane and a ketone containing enolic protons may yield an open-chain product, probably through a six-membered cyclic transition state [Eq. (46b)] 19). 

Nine-membered lactam rings can also be produced by the Beckmann rearrangement. The azonane ring 420 was selectively formed from an eight-membered cyclic ketone 419 by a rearrangement/reduction sequence (equation 175). 

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