Carbonyl and Thiocarbonyl Compounds

Compared with other synthetic intermediates, enolates show a decreased reactivity. The differences in reactivity are most striking in reactions with alkylating agents [1] and epoxides [6]. The reactivities of the various types of enolates towards alkyl halides decrease in the order C=C(0 )NR2 (amide-enolate) C=C(0 )0R (ester enolate) C=CO (ketone-enolate). Metallated nitriles, imines, and S,S-acetals are, in general, much better nucleophiles than enolates in alkylations and ft-hydroxyalkylations [1], Furthermore, the alkylation of aldehyde and ketone enolates usually does not stop after the mono-functionalization [12]. The decreased reactivity of (especially) aldehyde and ketone enolates also appears in thiolations with disulfides [2]. A solution of lithiated cyclohexanone in THF does not react at 20°C with CH3SSCH3 [1,2]. 

Enethiolates usually undergo S-alkylation with (primary) formation of S,S-, 0,S-, or N,S-acetals [3,4]. 

The chemistry of alkali enolates is subject of a number of extensive reviews [5-13]. The stereochemistry of directed aldol reactions with lithium enolates is discussed in the review of Mukaiyama [5]. 

Schuijl PJW, Brandsma L, Arens JF (1965) Reel Trav Chim Pays-Bas 85 1263 

Seebach D, (1988) Angew Chemie 100 1685 (1988) Angew Chemie Int ed (Engl) 27 1624 

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Organometallic betaines of type I can be considered as the closest structural analogs of carbon betaines of the (+ )P-C-C-X( ) type (IV), which were regarded for a long time as possible intermediates in classical reactions of carbonyl and thiocarbonyl compounds with phosphorus ylides (Wittig and Corey-Chaykovsky reactions and related processes,5,6 Scheme 1). Vedejs and coworkers7,8 proved unambiguously that oxapho-sphetanes (III) are true intermediates in the reactions of nonstabilized phosphorus ylides with carbonyl compounds. The formation of oxabetaines (+)p-c-c-o(-> was detected only in the form of their adducts with lithium salts.9,10... 

I.3.4.2.5. Carbonyl and Thiocarbonyl Compounds a-(Hydroxyimino)phenyl-acetonitrile oxide (generated in situ at room temperature from PhC( NOH)C ( NOH)Cl in the presence of NaHC03 or Et3N) reacts with simple aldehydes and ketones R1R2CO to give 1,4,2-dioxazoles 180 (347). Related dioxazoles, formed by cycloaddition of benzonitrile oxide to aromatic aldehydes, upon treatment with I-BuOK, undergo cyclo-reversion, allowing direct conversion to substituted benzoic acids or their esters (348). 

Metal-Oxygen Compounds. Trialkyltin alkoxides are remarkable for the variety of addition reactions they undergo with carbonyl and thiocarbonyl compounds. Bloodworth and Davies have reported reactions of tri-w-butyltin alkoxides with isocyanates, carbon dioxide, sulfur dioxide, isothiocyanates, carbon bisulfide, chloral, and ketene. The reactions observed were as follows ... 

Sila-ylides from complexation of silylenes by carbonyl and thiocarbonyl compounds have been observed their chemistry is discussed in Section V.A144. The first stable... 

TABLE 27. Structural effects on the gas-phase basicities of carbonyl and thiocarbonyl compounds X(CO)Y and X(CS)Y ... 

A direct comparison of structural effects on the GBs of carbonyl and thiocarbonyl compounds (summarized in Table 28) sets the stage for further discussions. 

Table 4., 3C Chemical Shifts3 and Total Charges6 of Carbonyl and Thiocarbonyl Compounds...

Some examples of the preparation of oxirancs, thiiranes and aziridines by the reaction of diazo compounds with trifluoromethyl-substituted carbonyl and thiocarbonyl compounds. imines,and oximes arc known. However, as noted in Section 2.1.1.6.2.5.1., carbenes are not always the reactive species. Thus, the reaction can consist of a 1,3-dipolar cycloaddition, followed by decomposition of the resulting pyrazolinc. 

The ene and Prins reactions are not mechanistically distinct. Coverage will therefore be organized by the nature of the carbonyl compound, with intermolecular reactions presented first, followed by intramolecular reactions. The emphasis will be on material published since the field has been reviewed " and on examples demonstrating the stereo-, regio- and chemo-selectivity of these reactions. Coverage is restricted to the addition of carbonyl and thiocarbonyl compounds to simple alkenes. Addition of carbonyl compounds to vinylsilanes, allylsilanes and enol ethers is covered in the following chapters. Addition of imines and iminium compounds to alkenes is presented in Part 4 of this volume. Ene reactions with alkenes and alkynes as enophiles are covered in Volume 5, Chapter 1.1. Use of aldehydes and acetals as initiators for polyene cyclizations is covered in Volume 3, Chapter 1.6. 

In addition to activated olefins, other double-bond substrates, such as carbonyl and thiocarbonyl compounds and azomethines have been used ( ). Likewise, heterocumulenes, such as carbon disulfide, isocyanates, isothiocyanates, carbodiimides, and N-sulfinylamines have been added to nitrile imides ( ). While usually reaction occurs across one of the cumulative double bonds, with carbon disulfide only the bis-adduct LVIII could be isolated ( ). 

Aliphatic Per- and Poly-fluorinated Carbonyl and Thiocarbonyl Compounds 129... 

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