1.3- dicarbonyl compounds reaction with tertiary

Conventional synthetic schemes to produce 1,6-disubstituted products, e.g. reaction of a - with d -synthons, are largely unsuccessful. An exception is the following reaction, which provides a useful alternative when Michael type additions fail, e. g., at angular or other tertiary carbon atoms. In such cases the addition of allylsilanes catalyzed by titanium tetrachloride, the Sakurai reaction, is most appropriate (A. Hosomi, 1977). Isomerization of the double bond with bis(benzonitrile-N)dichloropalladium gives the y-double bond in excellent yield. Subsequent ozonolysis provides a pathway to 1,4-dicarbonyl compounds. Thus 1,6-, 1,5- and 1,4-difunctional compounds are accessible by this reaction. 

Fig. 8 Iron-catalyzed coupling reactions of P-dicarbonyl compounds with ethers, sulfides or tertiary amines...

Tfce preferred synthetic route to these important intermediates is the Mannich reaction (Chapter 27), The compound is stored as the stable Mannich base and the unstable enone released by elimination of a tertiary amine with mild base, The same conditions are right for this elimination and for conjugate addition, Thus the aw-methylene compounds can be formed in the flask for immediate reaction with the enol(ate) nucleophile, The overall reaction from (3-amino carbonyl to 1,5-dicarbonyl appears to be a substitution but the actual mechanism involves elimination and conjugate addition,... 

Compared to diazonium salts, diazo compounds are generally much less reactive towards nucleophiles than towards electrophiles. As a result of this azo coupling reactions of diazo compounds are the exception rather than the rule. Electron withdrawing substituents on the diazo carbon increase the reactivity towards nucleophiles. Consequently the ability to undergo azo coupling reactions increases from diazomethane to diazocarbonyl- and 2-diazo-l, 3-dicarbonyl compounds. Among the earliest reactions known were those with cyanide and sulfite ions Tertiary phosphines, as opposed to amines, can form stable addition complexes with diazoalkanes probably due to the ability of phosphorus to stabilize the betaine with its empty d orbitals (6). 

Acetyl hypoiodite (iodine acetate), CH3COOI, is prepared by treatment of silver acetate in acetic acid with iodine at room temperature [779, 780], The reagent cleaves vicinal diols to dicarbonyl compounds [779] and degrades tertiary alcohols to ketones [780], Acetyl hypoiodite is also an intermediate in the reaction of alkenes with the so-called Simonini complex, an addition product of iodine with 2 mol of silver acetate [781, 782, 783],... 

In addition to the synthesis of jff-dicarbonyl compounds , the acylation of enamines also gives access to a wide variety of acyclic, carbocyclic and heterocyclic systems. The course of the reaction is often critically dependent upon the type of enamine used, on the substituents present in the two reagents, and on the experimental conditions, such as temperature, solvent, presence of added tertiary amine, etc. In contrast to alkylation, A acylation is readily reversible. Since enamines are stronger bases than the C-acylated enamines, half an equivalent of the enamine is lost by salt formation in their reaction with acid chlorides. This can be avoided by addition of a tertiary amine , but this in... 

The most investigated ctirbon nucleophiles are p-dicarbonyl or related enolates, generally cyclic in structure and fully substituted (i. e., tertiary) at the nucleophilic carbon. The products of reaction of these enolates with alkynyliodonium salts are p-dicarbonyl compounds, and their formation is mostly dependent upon the migratory aptitude of the substituent on the ethynyliodonium salt. 

The higher activity of primary amines in the reaction involving enones as Michael acceptors has also been extended to the use of different bifunctional catalysts (Scheme 3.19), which usually contain a primary amine functionality connected to a basic site by means of a chiral scaffold, as is the case in the use of 280 and 55. These diamine catalysts have been found to be excellent promoters of the Michael reaction of enones with cyclic 1,3-dicarbonyl compounds and malonates respectively, the tertiary amine basic site present at the catalyst structure being responsible for assisting in the deprotonation of the Michael donor in order to increase the concentration of the nucleophile species. In a different approach, bifunctional thiourea-primary amine catalyst 56a has also... 

The reaction of 2,3,4,5-tetrakis(trifluoromethyl)(yclopenta-2,4-dien-l-one with tertiary phosphines results in nucleophilic attack by the phosphine at carbonyl ojgrgen to form zwitterionic adducts. Nucleophilic attack at carbonyl ojgrgen is also implicated in a phosphine-mediated addition of 1,2-dicarbonyl compounds to nitroso-electrophiles. The diphosphine l,l-bis(diphenylphosphino)methane has been shown to undergo redox reactions with o-quinones, forming phosphine oxides of type (104). An overview of the reactions of HNO (azanone) with metal porphyrins includes reference to O-atom abstraction by phosphines from HNO to form nitrite. ... 

The best results with regard to solvents were obtained in water. The reaction is catalyzed by tertiary amines. The most efficient catalyst concerning yields, clear reaction, and selectivity is l,8-diazabicyclo[5.4.0]undec-7-ene (20 mol %). This transformation was expanded to several 1,3-dicarbonyl compounds. Due to the symmetry of acetylacetone 5 or dibenzoylacetone 134, identical products were formed by the ketalization step (133 Ri=R2=Me 136 Ri=R2=Ph Scheme 2.29). When used with unsymmetrical 1.3-dicarbonyl compounds, different products were formed via a regioisomeric ketalization step (reactions with benzoylacetone 138 in Scheme 2.29, 139 and 140 Ri=Me, R2=Ph) [44],... 

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