Nucleophilic addition vinylic systems

For trisubstituted olefins, the nucleophile attacks predominantly at the less substituted end of the allyl moiety, e.g. to afford a 78 22 mixture of 13 and 14 (equation 7). Both the oxidative addition of palladium(O) and the subsequent nucleophilic attack occur with inversion of configuration to give the product of net retention7. The synthesis of the sex pheromone 15 of the Monarch butterfly has been accomplished by using bis[bis(l,2-diphenylphosphinoethane)]palladium as a catalyst as outlined in equation 87. A substitution of an allyl sulfone 16 by a stabilized carbon nucleophile, such as an alkynyl or vinyl system, proceeds regioselectively in the presence of a Lewis acid (equation 9)8. The... 

In an investigation of the stereoselectivity of nucleophilic addition to larger ring systems, ethyl-, vinyl-, and ethynyl-lithium and -Grignard reagents have been added to 2-(3 -phenylpropyl)cycloheptanone (69). In all cases, the predominant product is the cw-alcohol, and calculations have been used to identify the steric and torsional effects in the transition state that favour this stereochemistry. 

The first reported controlled/living polymerization of p-methylstyrene with acetyl perchlorate in the presence of HBU4NCIO4 [221] was based on the added salt method. Later, it was reported that cumyl acetate/ BC13 and related initiating systems induce controlled/living polymerizations of p-methylstyrene [117,222] and 1,3,5-trimethylstyrene [223]. The HI/ZnC(2 system, suited for vinyl ethers and p-alkoxystyrenes, can also be used for p-methylstyrene [224], but the lower reactivity of the monomer requires a much higher concentration of the zinc activator (ca. 100 mJW for 10 mM HI) to obtain a sufficient polymerization rate. These systems function without added nucleophilic additives and can be classified under the counteranion method. 

The reaction of cyanomethyllithium with 2,4,6-tri-t-butylphenyl-dichlorophosphine enables a one-step preparation of the functionalised phospha-alkene (144). A new route to phospha-alkenes is provided by nucleophilic attack at the vinylic CH2 of the halogenophosphine (145), with displacement of halogen from phosphorus. Thus, with DABCO as nucleophile, the novel system (146) is formed.Treatment of the phosphino-substituted ylides (147) with Lewis acids results in the 2-phosphonio-l-phospha-alkenes (148), reported to be sufficiently stable for X-ray analysis, but also undergoing various addition reactions. 

The principally practicable route to allyl vinyl ethers by alkenation of allyl formates, has not yet been exploited in this context. In another approach, the nucleophilic addition of allylic alcohols to alkynic esters, one observes the exclusive formation of franr-enol ethers 2 the stereochemical information is lost, however, after the rearrangement, due to enolization of the formed formylacetic acid derivatives. On the other hand the nucleophilic addition of allyl alcohols to acceptor-substituted allenes like allenic sul-fones or phosphonates offers a novel route with fascinating potential. " Such systems that are readily... 

The acceleration of nucleophilic addition by a fluorine atom on the vinylic carbon can be applied for designing a microbial inhibition system. Scheme 2.23 shows a proposed mechanism for deoxy-amination of chorismate (28) via sequential Sf -type additions by... 

After an observation that carbon nucleophiles add to vinyl sulfone-modified hex-2-enopyranosides 35 and pent-2-enofuranosides 36 (Fig. 8.11) in a diastereo-selective fashion to the C2 carbon of the olefinic system from a direction opposite to that of the disposition of the anomeric methoxy group [8], Das et al. [9] undertook a study of the addition of carbon nucleophiles to vinyl sulfone-modified... 

Systematic studies of acetylenic vinylation of pyrroles in the system KOH/DMSO have shown that the reaction slows down in the presence of nitroxyl radicals and other inhibitors of radical processes [205,494]. This indicates a possibility of single electron transfer in nucleophilic addition of pyrroles to acetylene in superbase media. 

Abstract The formation of carbon-oxygen bond upon addition of O-nucleophUes to unsaturated molecules is very attractive as it represents an atom economical strategy to prepare a variety of saturated compounds from olefins and vinylic derivatives from aUcynes. Group 8 metals, especially ruthenium have provided an important contribution in this field. We report here on iron- and ruthenium-catalyzed addition of nucleophiles to unsaturated systems. As additions to alkenes are still scarce with these metals and the use of iron catalysts is limited, the main part of the chapter is dedicated to addition of carbamates, carboxylic acids, alcohols and water to triple bonds with ruthenium catalysts. 

The direction of addition, verified by acetylene oxidation into a known acid, proves that the nitiilimine carbon atom adds to the terminal atom of the enyne system, which is inconsistent with the assumed polarization of the unsaturated compound H2C=CH—C=C—R from the vinyl group towardR. The authors explain this by a possible transfer of the reaction center in nitrilimine as a particle with a nucleophilic center on a carbon Ph—C=N" —N —Ph Ph—C =N =N—Ph (63ZOB3558). 

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