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Acetylene derivs 1.3- dienes, synthesis

Ebdon and coworkers22 "232 have reported telechelic synthesis by a process that involves copolymerizing butadiene or acetylene derivatives to form polymers with internal unsaturation. Ozonolysis of these polymers yields di-end functional polymers. The a,o>dicarboxy1ic acid telechelic was prepared from poly(S-s tot-B) (Scheme 7.19). Precautions were necessary to stop degradation of the PS chains during ozonolysis. 28 The presence of pendant carboxylic acid groups, formed by ozonolysis of 1,2-diene units, was not reported. [Pg.380]

Dienes from 1,2,3-trienes via reductive carboxylation Synthesis of acetylene derivatives from 1,2,3-trienes Reductive alkylation... [Pg.464]

Diene synthesis with 5-vinyl-2,3-dihydro-1,4-dioxins Phenolether ring from acetylene derivs. via 2,3,4a,7-tetrahydro-1,4-benzodioxins... [Pg.131]

Intramolecular diene synthesis with acetylene derivs. [Pg.146]

Violent explosions which occurred at —100 to —180°C in ammonia synthesis gas units were traced to the formation of explosive addition products of dienes and oxides of nitrogen, produced from interaction of nitrogen oxide and oxygen. Laboratory experiments showed that the addition products from 1,3-butadiene or cyclopentadiene formed rapidly at about — 150°C, and ignited or exploded on warming to —35 to — 15°C. The unconjugated propadiene, and alkenes or acetylene reacted slowly and the products did not ignite until +30 to +50°C [1], This type of derivative ( pseudo-nitrosite ) was formerly used (Wallach) to characterise terpene hydrocarbons. Further comments were made later [2],... [Pg.1782]

If the alkenes and acetylenes that are subjected to the reaction mediated by 1 have a leaving group at an appropriate position, as already described in Eq. 9.16, the resulting titanacycles undergo an elimination (path A) as shown in Eq. 9.58 [36], As the resulting vinyltitaniums can be trapped by electrophiles such as aldehydes, this reaction can be viewed as an alternative to stoichiometric metallo-ene reactions via allylic lithium, magnesium, or zinc complexes (path B). Preparations of optically active N-heterocycles [103], which enabled the synthesis of (—)-a-kainic acid (Eq. 9.59) [104,105], of cross-conjugated trienes useful for the diene-transmissive Diels—Alder reaction [106], and of exocyclic bis(allene)s and cyclobutene derivatives [107] have all been reported based on this method. [Pg.346]

The authors elaborated an innovative synthesis of the Taxane core based on an intramolecular Diels-Alder reaction as the key step. The TBDMS-protected cylohexenone-derived alcohol was converted into the corresponding nitrile intermediate in five steps by known synthetic manipulations (Scheme 43), mainly based on transmetallation protocols. The diene handle for the Diels-Alder reaction was then introduced following a simple but highly efficient four-step procedure. The dienophile for the cycloaddition, the terminal acetylene moiety, was incorporated via lithiation chemistry to furnish the substrate for the intramolecular Diels-Alder cyclization (Scheme 43). [Pg.39]

Many other addition reactions of olefins, dienes, and acetylenes are known, which are catalyzed by metal carbonyls including Ni(CO)4, Fe(CO)5, and Co2(CO)8 and by carbonyl derivatives such as hydrocarbonyls or phosphine-substituted carbonyls. Among these are the hydro-carboxylation, hydroesterification, and hydrocyanation of olefins the synthesis of hydroquiniones from acetylenes, carbon monoxide, and water ... [Pg.15]

The synthesis of (5S,15S)-diHETE is shown in Scheme 4.16 and makes use of Pd-Cu coupling of a terminal acetylene to trans vinyl bromides (48 + 50 —> 51 and 51 + 49 — 52) to obtain eneynes. The acetylenes are reduced by catalytic hydrogenation to give the requisite cis-trans dienes. Acetylenes 46 and 47 bear the suitable optically active secondary alcohols for the (5S)and (155)-alcohol functions in the natural product and are derived from chiral reductions of the corresponding ketones. ... [Pg.239]

The naphthalene derivative shown, a possible intermediate for synthesis in the polycyclic field has been obtained by the Diels-Alder reaction between a vinyl bis-ketal derivative of cyclohexa-2,5-diene-1,4-dione and diethyl acetylene-... [Pg.284]

Most of the synthetic applications of retro-Diels-Alder reactions involve cyclopentadiene or furan derivatives, but there are other dienes that have appropriate functionality for this process. One example is illustrated by heating pyrone 102 in a sealed tube at 200°C with bis(trimethylsilyl)acetylene to give 103, after initial formation of cycloadduct 104 and loss of carbon dioxide via a retro-Diels-Alder reaction.The retro-Diels-Alder usually requires higher temperatures than the Diels-AIder reaction, and the normal Diels-AIder product can be obtained without competition from the retro reaction. When the retro Diels-AIder reaction is desired, flash vacuum pyrolysis is a common technique used in synthesis. " Retro-Diels-Alder reactions can also be catalyzed by Lewis acids (sec. 11.6.A).An example that uses furan as a retro-Diels-Alder synthon is taken from work by Cannone et al., who used the retro-reaction as a synthetic route to 4-substituted... [Pg.943]

Cycloadditions. The dienophilic properties of ( )-phenyl-sulfonyl-2-trimethylsilylethylene allow the preparation of adducts with reactive dienes such as cyclopentadiene and anthracene. The adducts are smoothly converted to alkenes upon treatment with fluoride ion, establishing the equivalence of the title reagent to acetylene. Alkylation of the a-sulfonyl carbanion can precede the elimination such that synthetic equivalents to HC CH, HC CD, and RC CH are available. The use of this reagent is highlighted by the synthesis of several functionalized dibenzobarrelenes (eq 1). The equivalency to DC CD and RC=CD is illustrated by the preparation of deuterated derivatives. [Pg.453]


See other pages where Acetylene derivs 1.3- dienes, synthesis is mentioned: [Pg.57]    [Pg.452]    [Pg.169]    [Pg.452]    [Pg.441]    [Pg.1026]    [Pg.235]    [Pg.392]    [Pg.470]    [Pg.364]    [Pg.517]    [Pg.331]    [Pg.161]    [Pg.34]    [Pg.24]    [Pg.29]    [Pg.205]    [Pg.494]    [Pg.229]    [Pg.375]    [Pg.152]    [Pg.8]    [Pg.155]    [Pg.112]    [Pg.87]    [Pg.329]    [Pg.119]    [Pg.176]    [Pg.2358]    [Pg.92]    [Pg.460]    [Pg.115]    [Pg.554]   
See also in sourсe #XX -- [ Pg.26 ]

See also in sourсe #XX -- [ Pg.26 ]




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1.3- Dienes acetylene derivs.

Acetylene derivatives dienes

Acetylene derivatives, synthesis

Acetylene derivs

Acetylenes synthesis

Acetylenic derivatives

Diene synthesis

Dienes, synthesis

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