Carbonyls and Thiocarbonyls

Exobidentate Coordination Dienic, Carbonyl, and Thiocarbonyl Derivatives... 

The second problem involves the measurement of pKa values for carbonyl and thiocarbonyl derivatives. Grieg and Johnson (157) have pointed out that the measurement of pKa values for very weak bases (11) is an inaccurate and arbitrary process. Of particular difficulty for our purposes is the fact that different carbonyl derivatives may require different acidity functions. As a result of this situation, no attempt was made to make correlations of pKa data for carbonyl and thiocarbonyl derivatives with eq. (2). Because accurate pKa values can be measured for imines, these values were correlated with eq. (2), although the conformational problem remains. The imine sets were first studied by Charton and Charton (73), who correlated them with eq. (2). No correlations of data for carbonyl or thiocarbonyl derivatives with eq. (2) are extant in the literature. Bhaskar, Gosavi, and Rao (158) have reported that AG values for complex formation of substituted thioureas with iodine are a linear function of the Taft a values. Drago, Wenz, and Carlson (159) have reported similar results for complex formation between iodine and substituted amides. Oloffson (160) has reported a linear relationship between -AH for the complex of substituted N,N-dimethylamides with SbCls and the ffj constants. 

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 ... 

The Molecules R2CXCR2 Including Azomethine, Carbonyl and Thiocarbonyl Ylides Their Syntheses, Properties and Reactions R. M. Kellogg, Tetrahedron, 1976,32,2165-2184. Thioureas in the Synthesis of Heterocycles T. S. Griffin, T. S. Woods and D. L. Klayman, Adv. Heterocycl. Chem., 1975,18, 100-158. 

Structures bearing carbonyl groups are generally more sensitive to base-catalyzed hydrolysis this is particularly true of the sulfones (73) which are readily ring opened to arene acids (74), aldehydes and ammonia. 2,4-Dioxo and thionyl derivatives behave similarly. Where both carbonyl and thiocarbonyl groups are present primary amines form imino derivatives by selective attack at the thiocarbonyl site in the dithioxo compound (75 X = S) reaction takes place at position 2 (Scheme 27) (79KGS291). 

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... 

Carbonyl and thiocarbonyl complexes of Mes2Si have been observed in a remarkable series of experiments by Ando and coworkers144. Photolysis of Mes2Si(SiMe3)2 was carried out at 77 K in a soft (3-MP/isopentane) matrix in the presence of tetramethyl-2-indanone or its sulfur analog. The free silylene was formed initially but it slowly reacted with the carbonyl (or thiocarbonyl) compound to give the complex, which can be formulated as a silacarbonyl ylide (Scheme 8). Further photolysis converted these ylide complexes to the silaoxirane or silathiirane, reversibly. 

TABLE 22. Comparison of changes in stretching frequencies for carbonyl and thiocarbonyl iridium(I) adducts0... 

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. 

Carbonyl and Thiocarbonyl Complexes.—For a comprehensive survey the reader should consult the Organometallic Specialist Periodical Report. 

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