General Reaction Patterns

The general reaction patterns of the benzoin condensation and the related Stetter reaction are depicted in Scheme 6.104. Both reactions are nucleophilic acylations,... 

Reduction Potentials and General Reaction Patterns of Group 14 Organometal Halides... 

The general reaction pattern for the reduction of group 14 organometal halides is shown in Eq. (45) [166]. The one-electron reduction of metal halides leads to the formation of the metal centered radicals. The metal radicals may undergo radical coupling to produce metal-metal bonds or addition to unsaturated compounds. The metal radical may also be reduced electrochemically under some conditions to give the metal anions, which react with electrophiles. 

Various other pathways not following a general reaction pattern start from preformed three-carbon chains and lead to cyclopropane systems. These include various metal-mediated rearrangements of saturated and unsaturated carbon skeletons. 

Allenes undergo facile carbopalladation and are used extensively in organic synthesis. The general reaction patterns of allenes with aryl halides are as follows. In carbopalladation of allene, an Ar group attacks the central sp carbon of the allene system to generate 367 and then the 7r-allylpalladium 368 as an intermediate. Then the attack of a nucleophile mainly on a less substituted terminus yields the alkene 369. Thus 1,2-addition to one of the double bonds in the allene occurs. In the absence of nucleophiles, y3-H elimination gives 2-substituted 1,3-dienes... 

The silicon-carbon double bond in intramolecularly donor-stabilized silenes is also extremely reactive. This is demonstrated by the reaction of (dichloFometfayl)tris(trimethylsilyl)silane with 8-dimethylaminomethyl-l-naphthyllithium, which deviates from the general reaction pattern. We expected to get another stable silene, but we obtained in a yield of 51 % the 1-sila-acenaphthene 13. Obviously, the silene 12 is unstable, and the silicon-carbon bond is inserted into one carbon-hydrogen bond of the benzylic methylene group (Scheme 5). 

The so-called secondary antioxidants X convert the hydroperoxides into innocuous non-radical compounds. Thus the chain branching by the start of new kinetic chain reactions is prevented. Therefore these substances are also called hydroperoxide decomposers. The general reaction pattern reads as ... 

Under similar reaction conditions, o-allylphenyltriflate reacts with vinylstannane to furnish the dicarbonylation product (Scheme 8).f Similar cascade carbonylation termination by organostannanes takes place with aryl iodides and seems to be a general reaction pattern. The reaction may be useful for the preparation of indanones possessing 2-oxoethyl groups at the 2-position (Scheme 8). ... 

In entry 9, the general reaction pattern from the DAST treatment of 1,2-0-iso-propylidene-a-D-glucofuranose and its derivatives with the OH-3 position free (or protected as an ether) is depicted. Besides the 8 2 product 100 [69], varying proportions of 3,6-anhydro compounds are additionally formed by IS[6,0-3] (when starting from a 3-benzyl ether, formation of benzyl fluoride is observed by NMR spectroscopy). In the case of the 3-acetate shown in entry 10, no NG participation but (to a minor extent) E[5,H-6] was observed [70]. 

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