1.2- dicarbony 1 compounds

Cyclization of a 2-aminoheterocycle by reaction with a 1,3-dicarbony compound is a widely used method for the synthesis of a fused pyrimidin-4-one (see also pp. 284-286). The conversion of 2-aminopyridine into a pyridopyrim-idinone by heating with an acetoacetate in the presence of a Friedel-Crafts reaction-type catalyst is typical PPA and PPE vary in their effectiveness from one reaction to another [2250, 2289, 2296]. This reaction is also catalysed by bases such as piperidine [2501]. 

Another route to five-membered rings from 1,4-dicarbony] compounds is summarised in the disconnection of (10) where the alkylating agent is derived from a dicarbonyl compound which may be available (see Table 25.1) or may have to be synthesised. 

The relationship between phenacylpyridinium cations and 1,3-dicarbony compounds has been pointed out (p. 330). In view of this similarity it is not surprising that these cations are split by alkali to give carboxylic acids ... 

Reaction conditions [a] alkyne (2equiv.), 1,3-dicarbony compound (1 mmol) Pd(PPh)3Cl2 (3mol%), dppp (6mol%), CO (14bar), [bmim][Tf2N]HOAc (2g) as solvent, llO C, 24h. [b] ( ) BINAP instead of dppp. 

Disconnection gives dihaloketonc (2) made from (3). This compound is best approached by the strategy we have often used for symmetrical ketones adding an activating group and using a 1,3-dicarbony i disconnection. There is a very similar example on p 329. ... 

Self-condensation of a-(Primary Amino) Carbonyl Compounds M. 1 2-Dicarbony I Compounds with a -Amino Acids... 

Ozonation of Alkynes. Reactions of alkynes with ozone afford either carboxylic acids or, if reductive procedures are used, a-dicarbony 1 compounds. For the production of carboxylic acids, MeOH has been shown to be superior to CH2CI2 as reaction solvent. As with alkenes, a number of reducing agents can be used to produce a-dicarbonyl compounds. An easy option which results in high yields of a-dicarbonyl compounds involves the addition of Tetracyanoethylene directly to an ozonation reaction mixture as an in situ reducing agent (eq 16). ... 

The direct nucleophilic substitution of electron-rich phenol ethers using hypervalent iodine oxidants in the presence of Lewis acid or fluorinated alcohols and involving aromatic cation-radical intermediates was originally developed by Kita and coworkers in 1994 [362], Since then this procedure with some variations has been extensively applied by Kita and other researchers for various oxidative transformations. In the intermolecular mode, this reaction (Scheme 3.122) has been utilized for the preparation of the products 298 from N3, AcO , ArS, SCN , 3-dicarbony 1 compounds and other external nucleophiles [320]. The oxidative coupling reaction in the intramolecular mode provides a powerful synthetic tool for the preparation of various... 

The functional equivalence of CpMo(CO)NO(T -allyl) to an allyl cation enables versatile decomplexation of the corresponding dicarbony allyl compounds. The reaction is generally conducted as a one-step synthesis without isolating the allyl cation. As shown in Scheme 11, treating 4 with NOBF in equimolar proportions, followed by addition of NaCH(COOMe)2 gives the chiral olefin that maintains the... 

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