Allene-1,3-diene

Besides alkoxy-, amino-, and amidocarbonylation reactions, a carbonylation process using a thiol as nucleophile, that is, thiocarbonylation, has been extensively studied.It has been shown that the thiocarbonylation takes place with 1-alkynes, " " " propargyl alcohols,allenes, " 1,3-dienes, propargylic mesylates, " and bicyclopropylidene . 

Within this class of compounds the reactivity of the M2(OR)6 compounds is particularly noteworthy. These have been shown to be templates for organometallic chemistry by the addition of unsaturated molecules such as CO, alkynes, ethene, allene, 1,3-dienes, a,/3-unsaturated ketones, etc.117 Some reactivity unique to di-... 

Numerous examples for the synthesis of cyclopropanes by [2-f 1] cycloaddition of photochemically generated acylcarbenes to alkenes, allenes, 1,3-dienes, and cycloheptatriene are given in Houben-Weyl Vol. 4/5b, pp 1158-1257 and in Vol. E19b, pp 1099-1107 and pp 1300-1303. 

Allenes, 1,3-dienes, cyclopropanes, cyclopropenes, and even acetylenes can also serve as the starting materials for 7r-allylpaUadium complexes. Some representative examples are given in Scheme 19. It is interesting to note that while sterically hindered t-BuC=CBu-t displaces the two ethylene ligands from [Pd(CH2=CH2)Cl2]2 to give the corresponding alkyne-Pd complex (Sect. B.ii, Table 5), sterically less hindered PhC=CBu-t reacts with the same Pd complex to generate a 7r-allylpalladium species (Scheme 19). ... 

The optimal proton donor to conquer this problem of regioselectivity is pivalic acid (2,2-dimethylpropionic acid). At room temperature, an allene diene ratio of 82 18 was observed, and at — 80 °C only the desired allene was formed146. 

The various products obtained from acetylenic diols 54 in the presence of acids suggest the formation and interconversion of acetylene-allene-diene cationoid intermediates (equation 18)33. The allene intermediates can be sometimes isolated and they were reported as participants in the acid-catalyzed reactions of alkynylpyrylium salts 55, a driving force of which is an aromatization of the pyrane ring (equations 19-21)34,35. 

The mechanism and stereochemsitry of dehydrohalogenations from vinyl halides have been extensively reviewed - It should however be pointed out that the effects of particular bases and solvents and of temperature cannot always be predicted with confidence as to rate of reaction and product distribution (acetylene, allene, diene). Therefore a variety of combinations of base, solvent and reaction conditions should be tried in order to obtain satisfactory results. 

Pudovik, S.L, and Aladzheva, I.M., Acetylene-allene-diene rearrangements of diphosphites with P,Y-acetylenic bond in the entire ester radical, Zh. Obshch. Khim., 33, 708, 1963 J. Gen. Chem. USSR (Engl. Transl.), 33, 702, 1963. 

Cumulated diene. S ee Allenes Dienes Cuprates. See Lithium diorganocuprates Curl, Robert E, 410 Curved arrows fishhook, 150... 

Allenic dienes having four different substituents possess chirality, as noted above the various possible modes of adsorption and the structures of products resulting from their hydrogenation have been explored. ... 

The groups capable of polymerization may be of different types, namely, vinyl, allyl, styryl, diene, allenic, acetylenic, acrylic, alkoxide, etc. Also, different rings bonded with metal such as epoxy, ethyleneimine, and others may be used. It goes without saying that multiple bond can be present not only as double bonds but also as triple, allene, diene bonds as well as their combinations. The correlation between the electronic structure and the... 

RXN17 Hydroboration, Hydrogermylation, Hydrosilylation and Hydrostannation of Alkynes, Allenes, Dienes and Enynes... 

The first type is the intermolecular variant of the reactions in Scheme 35 and has recently been thoroughly reviewed. Alkenes, allenes, dienes, and alkynes are suitable unsaturated coupling components for the carbopalladation. 

Wender et al. applied his Rh-catalyzed alkene-diene PK-type reaction described above to allene-dienes 374 and obtained similar results, wherein the proximal double bond of the allene moiety reacted exclusively to give bicyclo[3.3.0]octanones 375 (Scheme 2-28). It should be noted that the substitution pattern at the terminal carbon of the allene moiety has a significant effect on the reaction. 

Scheme 2-28. Rh- catalyzed allene-diene PK-type reaction.

Furthermore, the stereoselectivity at the bridged carbon could be controlled by using appropriate catalysts. For example, the reaction of allene-diene 502 catalyzed by a Rh-complex with ligand P[0CH(CF3)-(C6H40Me-2)]3 gave rrom-503 as the prominent product, whereas that with P[OCH(CF3)- C6H3(OMe)2-2,6 ]3/AgOTf afforded c/s-503 with excellent selectivity (Scheme 2-71). ... 

Pre-catalyst I and related gold phosphoramidite complexes also promote enantioselective intramolecular [4+2]-cycloadditions of allenic dienes/" This transformation was previously studied by Toste et who obtained the Diels-... 

Kanematsu and coworkers developed the intramolecular allene+diene Diels-Alder cycloaddition into a new indole synthesis (Scheme 24, equations 1, 2) [118-121], The allene functionality in 67 was prepared by homologation (HCHO, CuBr, i-Pr NH). This cycloaddition strategy was successfully applied to syntheses of hippadine (equation 2) [119], and ( )- and (+)-d5 -trikentrin B [120, 121],... 

The scope of hydroamination can be subdivided into the types of compounds containing N-H bonds that add to olefin or alkyne, or it can be divided into types of reagents containing carbon-carbon ir-bonds, such as alkenes, vinylarenes, dienes, allenes, and alkynes. Because the limitations of the catalysts and the rates of the reactions largely depend on the type of carbon-carbon Ti-bond involved in the reaction, this section of this chapter is divided into the reactions of alkenes, vinylarenes, allenes, dienes, and alkynes. 

A further example of a gold-catalyzed reaction where a strong influence of the electronic properties of the ligand used is observed is the gold-catalyzed cycliza-tion of the allene diene 19. In the presence of gold complexes bearing tt-accept-ing phosphite ligands, the [4-f 2]-cycloadduct 20 is formed almost exclusively. 

The principal synthetic value of these reactions is for synthesis of allenes, dienes, and other compounds, which would be difhcult to obtain under normal conditions. Entries 1-4, illustrate the use of the retro-ene reaction to produce different classes of organic compounds [28-31]. 

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