Synthesis from nonconjugated

A. Synthesis and Properties of Polymers from Nonconjugated Diynes. 983... 

Ho, S. C. H. Wu, M. M. Xiong, Y. Novel cyclopolymerization polymers from nonconjugated dienes and 1-alkenes. PCT International Patent Application WO 95/06669 (Mobil Oil Corp.), March 9,1995. Hustad, P. D. Coates, G W. Insertion/isomerization polymerization of 1,5-hexadiene synthesis of functional propylene copolymers and block copolymers. J. Am. Chem. Soc. 2062,124, 11578-11579. Hustad, P. D. Tian, J. Coates, G. W. Mechanism of propylene insertion using bis(phenoxyimine)-based titanium catalysts an unusual secondary insertion of propylene in a group IV catalyst system. J. Am. Chem. Soc. 2002,124,3614-3621. 

We present here examples of this condensation with an aromatic aldehyde and a cyclic ketone. Both of these examples are useful because, although other methods are available for their preparation, problems often attend these syntheses. In the synthesis of cyclohexy11deneaceton1tr11e, for example, the standard method results exclusively In the g.y-lsomer and none of the a,g-Isomer. In Part A of this procedure, cyclohexanone Is condensed with acetonitrile to give predominantly the conjugated Isomer (80-83%) whicfi is then separated from the nonconjugated isomer by selective bromination. 

Figure 13 shows the irreversible conversion of a nonconjugated poly (p-phenylene pentadienylene) to a lithiun-doped conjugated derivative which has a semiconducting level of conductivity (0.1 to 1.0 S/cm) (29). Obviously, the neutral conjugated derivative of poly (p-phenylene pentadienylene) can then be reversibly generated from the n-type doped material by electrochemical undoping or by p-type compensation. A very similar synthetic method for the conversion of poly(acetylene-co-1,3-butadiene) to polyacetylene has been reported (30), Figure 14. This synthesis of polyacetylene from a nonconjugated precursor polymer containing isolated CH2 units in an otherwise conjugated chain is to be contrasted with the early approach of Marvel et al (6) in which an all-sp3 carbon chain was employed.

The formation of spirocyclopropanes from the reaction of diazodiphenylmethane and ( )-8-phenylmenthyl esters of acrylic acid and methyl fumarate occurred with a modest level of diastereofacial selectivity (136). In contrast, diastereoselectivities of 90 10 were achieved in the cycloadditions of diazo(trimethylsilyl)methane with acrylamides 65 derived from camphor sultam as the chiral auxiliary (137) (Scheme 8.16). Interestingly, the initial cycloadducts 66 afforded the nonconjugated A -pyrazolines 67 on protodesilylation the latter were converted into optically active azaproline derivatives 68. In a related manner, acrylamide 69 was converted into A -pyrazolines 70a,b (138). The major diastereoisomer 70a was used to synthesize indolizidine 71. The key step in this synthesis involves the hydrogenolytic cleavage of the pyrazoline ring. 

A stereochemical study of the synthesis of unsaturated 1,4-aminoalcohols via the reaction of unsaturated 1,4-alkoxyalcohols with chorosulfonyl isocyanate revealed a competition between an retentive mechanism and an SnI racemization mechanism, with the latter having a greater proportion with systems where the carbocation intermediate is more stable.254 An interrupted Nazarov reaction was observed, in which a nonconjugated alkene held near the dienone nucleus undergoes intramolecular trapping of the Nazarov cyclopentenyl cation intermediate.255 Cholesterol couples to 6-chloropurine under the conditions of the Mitsunobu reaction the stereochemistry and structural diversity of the products indicate that a homoallylic carbocation derived from cholesterol is the key intermediate.256 l-Siloxy-l,5-diynes undergo a Brpnsted acid-promoted 5-endo-dig cyclization with a ketenium ion and a vinyl cation proposed as intermediates.257... 

Historically, the first example of l,4-(oxa/thia)-2-azole rings was described by Musante, in the late 1930s, who first correctly suggested the 5-imino-2-phenyl 1,4,2-oxathiazole structure 1 to the product obtained from the reaction of ammonium thiocyanate and benzhydroximoyl chloride <1938G331>. Also, the preparation and some properties of dioxazolones 2 described by Beck should be mentioned <1951CB688>, and also the synthesis of the first nonconjugated dioxazole derivative 3, from hydroxamic acid and benzophenone diethylacetal, described by Exner <1956CLY779>. 

It is then possible to reduce the nonconjugated double bond chemoselectively and add a pyridine nucleophile to the vinyl sulfone. Notice in this step that a lithium derivative can be prepared from a bromopyridine. In general, heterocycles form lithium derivatives rather easily. The skeleton of epibatidine is now complete and you will find some further reactions from the rest of the synthesis in the problems at the end of this chapter. 

Oxidation of a cyanohydrin derived from a conjugated aldehyde (as the 0-TMS derivative) using py-ridinium dichromate (PE)C) in DMF gave an a,3-unsaturated lactone (5 -butenolide) as the major product (equation 12). Simple nonconjugated cyanohydrins are not satisfactory substrates for the synthesis of acyl cyanides using PDC, because they seem to add to the initially formed acyl cyanides, leading ultimately to cyanohydrin esters. Oxidation of cyanohydrin to acyl cyanides can be carried out either by means of manganese dioxide, ruthenium-catdyzed oxidation with t-butyl hydroperoxide or NBS. ... 

Dolatkhani M., Cramail H., Deffieux A., Linear nonconjugated dienes from biomass as termonomers in EPDM synthesis,... 

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