Dicarbonyls, Group chains

The symmetry of (32) suggests addition of an activating group followed by 1,3-dicarbonyl disconnection to symmetrical (33). This is a 1,6-dicarbonyl compound but reconnection gives (34) with no obvious disconnections. An alternative is to work back to readily available (37) by FGA and chain extension. 

Bisphenol A, whose official chemical name is 2,2-bis(4-hydroxyphenyl)propane, is a difunctional monomer with two reactive hydroxyl groups, as shown in Fig. 20,2. It polymerizes svith dicarbonyl organic monomers, such as phosgene or diphenyl carbonate, which are illustrated in Fig. 20.3. During polymerization, shown in Fig. 20.4, the hydroxyl groups of the bisphenol A deprotonate in the presence of a base. After deprotonation, the oxygen atoms on the bisphenol A residue form ester bonds with the dicarbonyl compounds. The polymerization process terminates when a monohydric phenol reacts with the growing chain end. 

If the conjugated diene group is in the acyl chain of the acylcobalt carbonyl, then cyclization is possible. Thus, sorbylcobalt tricarbonyl triphenylphosphine on heating to 80°C., cyclizes to 2-methyl-7r-cyclopentenonylcobalt dicarbonyl triphenylphosphine (41). 

Interestingly, 2,3-dicarbonyl derivatives formed by the condensation of a-dicarbonyl compounds and 2-aminophenols (80JHC1625) exist in the 2Z/-form (81 Scheme 36). However, when there is an additional carbon atom in the side-chain of the 3-substituent so that hydrogen bonding with the NH group may now occur, as in the benzoxazinone (82), the equilibrium is directed strongly in favour of the 4Z/-tautomer (Scheme 37) (76JHC681). 

The compounds described in this section are diketones keto acids and keto esters, which may also be classified as dicarbonyl compounds, are considered in Section 5.14.3, p. 735. The relative location of the two carbonyl groups in the carbon chain may be designated numerically or by letters of the Greek alphabet. The alkyl groups may be the same or different the formulae below also represent keto aldehydes and dialdehydes when one or both of the residues (R), are hydrogen. 

Although l,8-naphthyridine-2,7-dicarbonyl chloride reacted with glycol to give di(2-hydroxyethyl)-l,8-naphthyridine-2,7-dicarboxylate (16) (excess HOCH2 CH2OH, 100°C 83%),1090 efforts to form a macrocyclic link between the carbonyl groups with a long-chain a,co-dihydroxy synthon proved unsuccess-... 

Open chain and cyclic thioacetals 1,3-Dithiolane and 1,3-dithiane derivatives are versatile intermediates in the synthesis and interconversion of monocarbonyl and 1,2-dicarbonyl compounds. Protection of carbonyl groups as their open-chain and cyclic thioacetals is an important method in the synthesis of organic molecules. Thioacetals are stable... 

Amino-l,2,4-oxadiazolcs (11) arc excellent sources of amidines. When they are treated with 1,3-dicarbonyl derivatives they are converted into enaminones (12), which cyclize to imidtizolcs in the presence of bases (Scheme 2.2.5). This reaction utilizes the well-known general attack of a nucleophilic group in the side chain at N-2 of the oxadiazole ring. Yields of 2-acylamino-4-acylimidazoles usually lie between 60 and 80% [21]. The free amino derivatives are readily isolated after acid hydrolysis. 

If the two -OH groups are on an open chain, two carbonyl compounds result. If the two -OH groups are on a ring, a single, open-chain dicarbonyl compound is formed. As indicated in the following examples, the cleavage reaction is believed to take place through a cyclic periodate intermediate. 

A similar dramatic influence of ionic liquid was also reported by Ranu s group in the Michael reaction of active methylene compounds with methyl vinyl ketone and methyl acrylate in the presence of an ionic liquid, 1-butyl-3-methylimidazolium hydroxide ([bmImjOH). Interestingly, open-chain 1,3-dicarbonyl compounds reacted with methyl vinyl ketone and chalcone to give the usual monoaddition products, whereas the same reactions with methyl acrylate or acrylonitrile provided exclusively bis-addition products (Scheme 5.55). 

Functional groups or side chains of pyridazines have been used in the formation of new heterocyclic rings. Hydrazinopyridazines, when condensed with 1,3-dicarbonyl compounds give JV-pyridazinylpyrazoles. Azido-pyridazines and acetylenes give triazolylpyridazines on which various re-... 

Apart from phosphanes, typical systems used as chiral ligands in catalysis are alcohols, amines, amino alcohols and other N-functionalities including imines, amides and N-modificd carbonyl groups. Dicarbonyl compounds and their chirally modified equivalents such as dioximes or crown ethers, as well as sulfoxides, arsines, and cyclopentadienyl ligands with chiral side chains have been used. 

A considerable contribution to oin knowledge of the chemistry of dicarbonyl sugars, a group of sensitive and reactive compounds, has been made by Theander, who used, for the most part, acetals of D-glucose, D-mannose, and n-galactose. Carbonyl derivatives of aldoses and aldosides are of importance in the synthesis of branched-chain sugars. ... 

A -Acyl substitution of 2-amino-2-deoxyaldohexoses prevents their reaction with /3-dicarbonyl compounds from giving pyrrole derivatives. Instead, the products of the aldol reaction of the aldehydo form of the sugar with the active methylene group of the /3-dicarbonyl compound are formed. These substances have the structural features of higher-carbon, branched-chain carbohydrates. 

In the reactions of 2-amino-2-deoxy-D-glucose with some /3-dicarbonyl compounds (such as ethyl acetoacetate, 2,4-pentanedione, or pyruvic acid) in alkaline solution, pyrroles lacking the tetrahydroxybutyl chain are obtained. The loss of this group cannot occur with the already formed (tetrahydroxybutyl)pyrroles, because these compounds, as exemplified by 3-acetyl-2-methyl-5-(D-ora wo-tetrahydroxybutyl)pyrrole (2), remain unchanged at the pH (9-10) of the reaction. The fission of the sugar chain most probably occurs for one of the intermediates of the reaction, for instance (79), and it may be formulated as a concerted-elimination reaction catalyzed by the hydroxyl ion, as indicated in Scheme C. The... 

---