Cleavage nucleophilic

Chemical Properties. The most impoitant reactions which tetraorganotins undergo are heterolytic, ie, electrophilic and nucleophilic, cleavage and Kocheshkov redistribution (81—84). The tin—carbon bond in tetraorganotins is easily cleaved by halogens, hydrogen hahdes, and mineral acids ... 

When the reaction of perfluQro-3,4-dimethyl-3-hexene with methanol is performed in the presence of pyridine, a perfluorinated dihydrofuran is formed, probably by a process involving generation of an anionic oxygen atom by nucleophilic cleavage of a supposed intermediate ether [27] (equation 24)... 

Previous reviews on the chemistry of isoxazole dealt primarily with the synthetic routes and the nucleophilic cleavage of isoxazole derivatives. The first part of the present review is concerned with new investigations in the synthetic field, but the main attention is devoted to a study of the properties of isoxazoles. The review covers studies undertaken during this decade though some earlier works are mentioned when necessary. No complete coverage of the chemistry of partly or fully reduced isoxazoles and their oxo derivatives is attempted, but those aspects of the chemistry of isoxazolines and isoxazolidines that are closely related to the problems under discussion are also mentioned. 

It was not until 1940 that the sulfonation of alkylisoxazoles by heating them with chlorosulfonic acid was reported. This gave a mixture of isoxazole-4-sulfonic acids (58) and their acid chlorides (59). The position of the sulfonic group in derivatives of monomethyl isoxazoles has been proved by nucleophilic cleavage of the isoxazole ring (60 61). Recently it proved possible to sulfonate isoxazole... 

It has been shown that hydroxymethylene cyclohexanones, in contrast to their cyclopentanone analogs, can be smoothly converted into a-cyanocyclohexanones by the nucleophilic cleavage of the correspond-... 

The mechanism of the nucleophilic cleavage of the isoxazole nucleus can now be considered as well understood. The first stage of almost all variants of this reaction consists in the removal of the proton by the nucleophile from the unsubstituted carbon atom with the lowest electron density of the isoxazole ring, usually C-3 or C-5. Neutralization of the negative charge of the resulting isoxazolyl anion causes the... 

Decarboxylation of isoxazole-3-carboxylic acids is related to the nucleophilic cleavage of the isoxazole ring as far as the nature of the reaction products is concerned. It occurs at temperatures above 200°C and is accompanied by the cleavage of the nitrogen-oxygen bond of the heterocyclic ring to yield a j8-ketonitrile. It was first reported by Claisen with 5-methyl- and 5-phenyl-isoxazole-3-carboxylic acids (153- 154).Under the reaction conditions, j8-ketonitriles condense... 

There is just the possibility that in adding bromine to butadiene the 1,4-adduct might be obtained via an unstrained, five-membered cyclic bromonium ion (70). This would lead, on nucleophilic cleavage by Bre, to the cis 1,4-dibromide (71) ... 

The increasingly common theme of developing new pyrrole syntheses that involve cyclopropane fragmentations appeared in a type Ilae pyrrole synthesis <06OL835>. Treatment of doubly activated cyclopropane 43 with benzylamine in the presence of magnesium sulfate led to complex pyrrole 44 via a nucleophilic cleavage of the cyclopropane ring, intramolecular condensation, and isomerization of the exocyclic JC-bond. 

Only the appearance of the rearranged product is significant for benzocyclopropenone intermediacy, since the indazolone 168 was detected and trapped by tetra-cyclone via 170 in the oxidation of 167, which was shown to yield only unrearranged ester 169 by nucleophilic cleavage by the solvent thus 168 cannot be a precursor of benzocyclopropenone 171. 

Reductive nucleophilic cleavage of the l-alkoxymethyl-6,8-dioxabicyclo[3.2.11-octanes 44 catalysed by TiCl4 leads to the formation of the oxepane derivatives 45 (eg. R = Me) in good yield <00T1065>. 

When Wacker-type reactions are performed under a CO atmosphere, the (3-H elimination pathway can be suppressed in favor of CO insertion and subsequent nucleophilic cleavage of the acyl metal species.399 This alkoxycarbonylation process has found widespread utility, particularly in the synthesis of five- and six-membered oxacyclic natural products. For example, the THF core of tetronomycin was prepared by the Pd-catalyzed alkoxycarbonylation of 4-alkenol derivatives (Equations (117) and (118)), where stereocontrol was achieved by utilizing either the directing ability of a free hydroxyl or the conformational bias imposed by a bulky silyl ether.420 Additional examples making... 

Allylic amination is important for the solid-phase organic synthesis.15 The solid-phase allylic aminations are devised into the G-N bond formation on solid support and the deprotection of allyl ethers. As a novel deprotection method, the palladium-catalyzed cyclization-cleavage strategy was reported by Brown et al. (Equation (4)).15a,15b The solid-phase synthesis of several pyrrolidines 70 was achieved by using palladium-catalyzed nucleophilic cleavage of allylic linkages of 69. 

Nucleophilic cleavage of hexaphenyldiplumbane by potassium tert-butoxide results in the formation of the plumbyl anion K+PbPh3, which is principally characterized by the high field shift of the C-l nuclei to 191.11 ppm in the NMR spectrum hexaphenyldigermane and hexaphenyldistanne behave analogously.30... 

Nucleophilic cleavage, acid catalyzed hydrolysis, and oxidation of aldicarb in dilute solution were achieved in batch and/or column experiments using macroporous reactive ion exchange resins. As in solution, nucleophilic cleavage proceeds faster than acid catalyzed hydrolysis. The basis for pursuing study of the latter mechanism is discussed. 

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