Synthesis using Simple Olefins

Synthesis using Simple Olefins.—1,3-DipoIar reagents and the classical Diels-Alder addition of dienes both usually require activated olefins, and few enophiles are known which readily cycloadd to isolated double bonds. Such an avid enophile is the A -alkyl-iV-vinylnitrosium ion (447), generated in situ by silver(i)-induced ionization of a-chloronitrones (448). Cycloaddition 

A combination of [4 + 2] cycloaddition and [2,3]-sigmatropic rearrangement has been used with effect in the synthesis of hasubanan derivatives. Thus the 1-butadienyl phenyl sulphoxide (456) reacts with the enamine (457) to yield (458) as a mixture of diastereoisomeric sulphoxides. Heating (458) in the presence of a thiophilic species drives the equilibrium over to the sulphenate ([2,3]-sigmatropic shift) as the latter is converted into the amino-alcohol (459). This annelation sequence may also be used with electron-deficient dienophiles by employing 1-butadienyl phenyl sulphide (460).  

Reaction of phosgene with iViV-dialkylisobutyramides followed by elimination of hydrogen chloride gives x-chloroenamines (461). In contrast to ordinary vinyl halides, these substrates show high reactivity towards nucleophilic reagents, particularly on addition of silver ion. Thus electron-rich 

The reagents (468), (469), and (470) are keten equivalents since they undergo Diels-Alder addition to dienes and the disguised carbonyl group may be subsequently exposed. (Keten itself usually prefers [2 + 2] addition.) A comparison between (468), (469), and (470) for regioselective synthesis of bicyclo[2,2,2]octenenones (471) shows that 2-chloroacrylonitrile is superior in this respect and is also the most reactive.  

Reaction of the trans-aWylic alcohol (472) with 1-dimethylamino-l-meth-oxyprop-l-ene gives the erythro-am d (473) and the m-allylic alcohol gives 

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Pentacyclosqualene, the symmetrical hydropicene corresponding to squalene, has not been made by acid-induced cation-olefin cyclization of squalene, despite considerable experimental study. A simple, convergent synthesis of pentacyclosqualene using cation-olefin cyclization to generate ring C was developed. The Cjo-framework was constructed by radical coupling to a tetracyclic intermediate that was also used for the synthesis of onoceradiene. 

He was a Professor of Industrial Chemistry, School of Engineering, Polytechnic Institute of Milan, Milan, Italy since 1937. He became involved with applied research, which led to the production of synthetic rubber in Italy, at the Institute in 1938. He was also interested in the synthesis of petrochemicals such as butadiene and, later, oxo alcohols. At the same time he made important contributions to the understanding of the kinetics of some catalytic processes in both the heterogeneous (methanol synthesis) and homogeneous (oxosynthesis) phase. In 1950, as a result of his interest in petrochemistry, he initiated the research on the use of simple olefins for the synthesis of high polymers. This work led to the discovery, in 1954, of stereospecific polymerization. In this type of polymerization nonsymmetric monomers (e.g., propylene, 1-butene, etc.) produce linear high polymers with a stereoregular structure. 

Various papers describe the aqueous biphasic hydroformylation for simple olefins as well as for functionalized olefins or dienes [154-174] (cf. the Section 6.1). In recent work [175], the synthesis of n-nonanal by consecutive isomerization and hydroformylation reactions of trans-4-octene has been described. The catalyst used was the in situ combination of Rh(acac)(CO)2 and the chelate phosphite BIPHE-PHOS. Performing the reaction in propylene carbonate the selectivity to n-nonanal could be raised up to 95%. If after the reaction the product is extracted with dodec-... 

Derivatives of oleic acid that imdergo cross-metathesis with simple olefins are listed in Table 9.4, while Table 9.5 gives some examples of cross-metathesis reactions of simple olefins with other functional olefins. Such cross-metathesis reactions may provide useful routes to speciality chemicals such as synthetic perfumes, insect pheromones (Crisp 1988), prostaglandin intermediates (Dalcanale 1985), etc. (see Mol 1982, 1991). Of special interest are ethenolysis reactions, which allow the synthesis of compoimds with terminal double bonds. Ethenolysis (and cross-metathesis with lower olefins) has been investigated extensively for... 

The ketenes are prepared by modifications of the general methods for the synthesis of olefins. The ketenes are much more reactive than simple olefins, however, and are more likely to enter into combination with the reagents from which they are prepared or with the solvents used or into self-condensation to yield dimers or polymers. Many of the aldoketenes, which generally are more reactive than ketoketenes, have not been isolated as the pure monomers. The dimers of aldoketenes (p. 127) have some of the properties of ketenes, and certain of them are useful reagents. 

HWE olefmation has applied in the synthesis of simple and functionalized a,P-unsaturated nitriles. Scettri and co-workers have developed a practical procedure for HWE olefination of aldehydes 3 and ketones 33 with a-cyano phosphonates 30 using lithium hydroxide as a mild... 

In this review, the synthesis of SF5-olefins and acetylenes and their conversion to compounds with new functional groups are described. It will be seen that there are only few reactions that allow the introduction of an SF5-group, and that there are also only few reactions which lead to derivatives of unsaturated compounds. The chemical transformations of these simple unsaturated compounds into a number of useful and exciting products will be described. 

The present procedure, based on the last method, is relatively simple and uses inexpensive starting materials. Step A exemplifies the 2 + 2 cycloaddition of dichloroketene to an olefin, " and the specific cycloadduct obtained has proved to be a useful intermediate in other syntheses. Step B has been the subject of several mechanistic studies, and its yield has been greatly improved by the isolation technique described above. This synthesis has also been extended to the preparation of various tropolone derivatives. " ... 

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