Protection for the Carbonyl Group

0-Methyl-5-2-(methylthio)ethyl, 209 Cyclic Monothio Acetals and Ketals 

The carbonyl group forms a number of other very stable derivatives. They are less used as protective groups because of the greater difficulty involved in their removal. Such derivatives include cyanohydrins, hydrazones, imines, oximes, and semicarbazones. Enol ethers are used to protect one carbonyl group in a 1,2- or 1,3-dicarbonyl compound. 

Although lUPAC no longer uses the term ketal, we have retained it to indicate compounds formed from ketones. 

Derivatives of carbonyl compounds that have been used as protective groups in synthetic schemes are described in this chapter some of the more important protective groups are listed in Reactivity Chart 5.  

See also H. J. E. Loewenthal, Protection of Aldehydes and Ketones, in Protective Groups in Organic Chemistry, J. F. W. McOmie, Ed., Plenum Press, New York and London, 1973, pp. 323-402. 

Dimethyl, 297 Diisopropyl, 304 Bis(2,2,2-trichloroethyl), 305 Dibenzyl, 305 Bis(2-nitrobenzyl), 305 Diacetyl, 306 

3- Dioxanes, 308 5-Methylene-1,3-dioxane, 310 5,5-Dibromo-1,3-dioxane, 310 5-(2 -Pyridyl)-1,3-dioxane, 311 5-Trimethylsilyl-1,3-dioxane, 311 

3- Dioxolanes, 312 4-Bromomethyl-1,3-dioxolane, 322 4-(3-Butenyl)-1,3-dioxolane, 323 4-Phenyl-1,3-dioxolane, 323 4-(4-Methoxyphenyl)-1,3-dioxolane, 324 4-(2-Nitrophenyl)-1,3-dioxolane, 324 4-Trimethylsilylmethyl-1,3-dioxolane, 324 

5- Dimethyl-1,3-dioxolane, 326 frans-1,2-Cyclohexanediol Ketal, 327 frans-4,6-Dimethyl-1,3-dioxane, 327 

O-Trimethylsilyl-S-alkyl, 344 O-Alkyl-S-alkyl or -S-phenyl, 345 0-Methyl-S-2-(methylthio)ethyl, 346 

5- Tetramethyl-1,3-dioxolane, 466 4-Bromomethyl-l, 3 -dioxolane, 467 4-Phenylsulfonylmethyl-l,3-dioxolane, 467 4-(3-Butenyl)-l,3-dioxolane, 468 4-Phenyl-l,3-dioxolane, 468 

4- (4-Methoxyphenyl) -1,3 -dioxolane, 468 4- (2-Nitrophenyl) -1,3 - dioxolane, 469 4- (4-Nitrophenyl) -1,3-dioxolane, 469 4-Fluorous-l,3-dioxolane, 469 

4-[6-Bromo-7-hydroxycoumar-4-yl]-l,3-dioxalane (Bhc-diol) Ketal, 470 4-Trimethylsilyl-l,3-dioxolane, 470 0,0 -Phenylenedioxy Ketal, 470 

Greene s Protective. Groups in Organic Synthesis, Fourth Edition, by Peter G. M. Wuts and Theodora W. Greene 

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Reactivity Chart 5. Protection for the Carbonyl Group (Continued)... 

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