Ketones, addition derivatives

Only few allyltitanium reagents bearing a removable chiral auxiliary at the allylic residue are known. The outstanding example is a metalated 1-alkyl-2-imidazolinone14, derived from (—)-ephedrine, representing a valuable homoenolate reagent. After deprotonation by butyllithium, metal exchange with chlorotris(diethylamino)titanium, and aldehyde or ketone addition, the homoaldol adducts are formed with 94 to 98% diastereoselectivity. 

R. S. E. Conn, A. V. Lovell, S. Karady, L. M. Weinstock, Chiral Michael Addition Methyl Vinyl Ketone Addition Catalyzed by Cinchona Alkaloid Derivatives , J. Org Chem. 1986, 51, 4710-4711. 

Robinson Annulation The addition of a methyl vinyl ketone (or derivative) to a cyclohexanone to form an a, 5-unsaturated ketone containing a six-membered ring. 

In addition to the parent ketones, some derivatives (such as the 2,4-dini-trophenylhydrazones and p-tolylsulfonylhydrazones) have been prepared by the same authors, and this work was covered by a patent.211... 

At an early date it was already recognized that the ketone (IX) derived from an oxidation of the C-18 carbinol function of methyl reserpate could be of considerable utility for further transformation of the reserpine pentacyclic ring system, but early attempts at the preparation of the desired compound by conventional oxidation, e.g., by Oppenauer s method, AAchlorosuceinimide, sodium dichromate, or chromic oxide in pyridine, were unsuccessful with both methyl reserpate and methyl 18-epireserpate. The ketone was finally obtained by heating methyl reserpate p-bromobenzene sulfonate with dimethyl sulfoxide in the presence of triethylamine (162), a method successfully used for simpler compounds (163). Subsequently, it was found that this oxidation could also be realized with other benzene sulfonate esters of methyl reserpate and 18-epireserpate. That the stereochemistry of the molecule was unaffected was proved by sodium borohydride reduction of the ketone, which gave equal amounts of methyl reserpate and its 18-epimer. This and other simple reactions of the ketone are sketched in Chart III, and additional observations will be given. 

In contrast to the -enolates derived from cyclic ketones, addition of propiophenone trichlorosilyl enolate (Z)-21 to aldehydes requires longer reaction times and higher loadings of catalyst. Although the yields of the aldol products remain high, both the diastereo- and enantioselectivities are attenuated as compared to their E counterparts (eq 9, Table 8). 

A number of addition derivatives may be used in the identification of the carbonyl compounds. Of these the crystalline derivatives formed with phenylhydrazine, C6H6NHNH2, and hydroxylamine, NH2OH, are the most important. The products formed with phenylhydrazine are called phenyUiydrazones, and have the general formula, RRiC=NNHC jls. The products formed with hydroxylamine are called oximes, and have the general formula, RRiC=NOH. Other crystalline addition compounds are formed with sodium bisulfite by aldehydes, and by those ketones which contain a methyl group. The addition compounds with ammonia, except in the case of acetaldehyde and a few other carbonyl compounds, are complex products. 

Cyclopropene underwent cycloaddition to tropylium perchlorate in aqueous dioxane at 20 °C to give an oily alcohol oxidation with chromic acid gave predominantly the ketone 4 derived from endo addition. ... 

The particular behavior of the ketone/silane derivative/additive combination proposed as an efficient photoinitiating system under air (better than the reference ketone/amine/additive system) was shown in Ref. [128]. 

Chiral -substituted carbonyl compounds have been prepared in high optical purity (64-98%) by the use of organoaluminium chemistry. Thus treatment of an acetal derived from an a, 6-unsaturated aldehyde and R,R- tartaric acid diamide with a trialkylalane gives largely the 1,4- addition product from which the desired ketone is derived by ozonolysis (Scheme 12). 1... 

CTarbazoles can be derived from the acid-catalyzed intramolecular addition of the ketones (117) derived from gramine and oxomalonate systems (116) <88TL6505> (Scheme 33). Treatment of the ketone (118) with one equivalent of n-butyllithium followed by one equivalent of methyllithium and then borohydride reduction of the intermediate diol gave the pyridocarbazole (119). The transformation involves intramo<< ular trapping of the intermediate ddehyde at C-3 (Equation (30)) <83TL3831>. 

Chapter 18 discussed the acyl addition reactions of several nucleophiles with the carbonyl unit of aldehydes and ketones. As pointed out in Chapter 16, carboxylic acids and their derivatives also contain a carbonyl unit. Although these acid derivatives react with nucleophiles via attack at the acyl carbon, the presence of a leaving group attached to the acyl carbon leads to a subsequent reaction that is not possible with aldehydes and ketones. Acid derivatives react with nucleophiles via acyl substitution. This reaction pathway proceeds by an intermediate called a tetrahedral intermediate. The introduction to this reaction, presented in Chapter 16 (Section 16.8), will be explained and expanded here. 

In 1971 at the University of Strathclyde in Glasgow, Professor Peter Pauson reported on the retro-Diels-Alder reaction of norbomadiene 3 induced by dicobalthexacarbonyl complexes of acetylene or phenylaeetylene 1 to provide dicarbonylcyclopentadienylcobalt complexes 4 in high yield. Almost as an after thought, he mentions In addition to the above products, the reaction of norbomadiene with complexes 1 yields hydrocarbon and ketonic products derived from norbomadiene, acetylene and carbon monoxide. ... 

Highly hindered bases such as (20) deprotonate the methyl group of methyl ketones specifically. In the presence of an aldehyde, aldol reaction occurs before enolate equilibration can take place. The same base promotes the addition of ester and lactone enolates to aldehydes and ketones. However, it has been noted that at low temperature (—70 °C), the more accessible lithium diethylamide deproto-nates only the methyl group of methyl ketones. Addition of a second aldehyde or ketone species at this temperature leads to the exclusive formation of jS-ketoIs derived from this enolate. ... 

The carbonyl group of acid derivatives reacts with the nucleophilic carbanion available from organo-metallic reagents. However, the reactions of the individual classes of compounds are not as straightforward as the addition reactions of organometallic compounds with aldehydes and ketones. Addition of a carbanion to the acyl carbon atom generates a tetrahedral intermediate that can decompose to give a ketone that will react further with another equivalent of the carbanion. 

The reactions leading to 3 -phosphonylated nucleosides require addition of a deprotonated H-phosphonate to the appropriate ketones 45, derived from natural nucleosides (Scheme 47.11). These reactions usually proceed with complete stereoselectivities. " However, a subsequent removal of the a-hydroxyl group under radical reaction conditions... 

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