Reaction at the Carbonyl Group

The reaction with organolifliium and Grignard compounds have found widest application in the preparation of tertiary [l- C]alcohols and tertiary [l- C]amines . With MeLi or p-chlorobenzylmagnesium chloride, for example, the respective tert- - C -alcohols 247 and 248 were obtained, which upon treatment with benzyl or sodium cyanide gave the amides 249 and 250 in an acid-catalyzed Ritter reaction. Subsequent hydrolytic 

The synthesis of rrani-[13- C]retinoic acid (265) (Procedure B) may serve as an additional example of the use of an [ C]acetone-based building block. Homer-Wads-worth-Emmons olefination of [2- C]acetone with methyl diethyl-phosphonoacetate afforded methyl 3-methyl-2-[3- C]butenoate t2631. Upon deprotonation, this coupled with /3-ionylideneacetaldehyde (264) to provide 265. thereby extending the carbon skeleton of 264 again by a labeled five-carbon unit Building block 263 was also shown to be accessible (Procedure C) through Reformatsky synthesis of [2- C]acetone with zinc and 

Nitrogen nucleophiles such as hydroxylamine and isopropylamine react with [ C]-acetone to give the corresponding oximes or imines, which can be readily reduced with 

281a (S)-n C1CGP12388 281b ISl-P Clexaprolol 281c (S)-[ C]bisoprolol 

Treatment of [1,3- C]acetone with semicarbazide affords the respective semicarba-zone, which was decomposed following the Huang-Minlon protocol to give [1,3- C] 

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Reactions at the carbon-nitrogen double bond of iminium salts are analogous to nucleophilic reactions at the carbonyl group of aldehydes and ketones. This is why free enamines do not react with nucleophilic reagents, whereas their salts can undergo such reactions. 

When substituted quinones undergo reaction at the carbonyl groups, the substituent does not exert the same effect on each carbonyl group. Consider, for... 

Compound 63, the 2-formyl derivative of compound 61, undergoes a series of side-chain reactions at the carbonyl group including reduction with sodium borohydride and condensation reactions with hydroxylamine or malononitrile. The reactions afford the appropriately 2-substituted products in excellent yields <2004CHE1477>. 

Reactions at the Carbonyl Group 1,2-Additions of Organometallic Compounds ... 

As with reactions at the carbonyl group, weakly basic leaving groups are more readily displaced than strongly basic ones. 

An important example of this type of reaction is the formation of esters, which was discussed previously in connection with the reactions of alcohols in Section 15-4D. Similar addition-elimination mechanisms occur in many reactions at the carbonyl groups of acid derivatives. A less obvious example of addition to carboxyl groups involves hydride ion (H 0) and takes place in lithium aluminum hydride reduction of carboxylic acids (Sections 16-4E and 18-3C). 

Unsaturated aldehydes, ketones and esters undergo hydroformylation of die double bond without reaction at the carbonyl group. For example, dienes yield aldehydes in a stepwise fashion (vide supra) however, a,(3-unsaturated aldehydes and ketones undergo rapid hydrogenation to the saturated aldehyde... 

There is a fundamental relationship between the mechanisms of the reactions at the carbonyl group introduced so far. In each case, a nucleophile or Lewis base attacks the positive end of the carbonyl group. And, in each case, the rate of reaction can be increased by coordinating a Lewis acid or electrophile at the other end of the carbonyl. 

The reaction of 15 with hydrazine indicates two possibilities for nucleophilic attack at 4-azaazulenones 4-8 (1) reaction at the carbonyl group and... 

Review Unit 8 Carbonyl Compounds 1. Reaction at the Carbonyl Group... 

Reactions at the carbonyl group—Adding or removing one carbon atom... 

Reactions at the Carbonyl Group—Adding or Removing One Carbon Atom... 

General acid-catalyzed nucleophilic displacement reactions at the carbonyl group (equation 5) are also known to occur, but less is known... 

This review focuses on free radical-mediated stereoselective bond construction in which the carbonyl group plays a key role. Reaction at the carbonyl group as well as on carbons alpha and beta are described. The general reaction characteristics of these reactive intermediates are as follows. The acyl radicals are nucleophilic in character and thus they react easily with electrophilic acceptors. On the other hand, radicals on carbon alpha to the carbonyl are electrophilic in nature and their reactivity matches with nucleophilic partners. The majority of reactions at carbon beta to the carbonyl are in a, -unsaturated systems and in these the beta carbon is electrophilic. 

Reactions of 1,3-dichloropropanone with Grignard reagents leads to initial reaction at the carbonyl group followed by reductive 1,3-dechlorination on treatment with lithium powder to give cyclopropanols 35 in moderate yield. ... 

Several reports of the additions of phosphites and phosphoramidites to carbonyl groups have appeared. In the case of aminophosphines, these involve the well-documented rearrangement to the a-amino-compound (23), and for the vinyl ketone (24) the product is (25), reaction at the carbonyl group competing favourably with Michael addition (Scheme 5). The already extensively studied, but still some-... 

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