4.4- bis-functionalized 1,6-diene

Keywords active methylene compound, unsaturated alkyl halide, alumina, potassium tert-butoxide, 4,4-bis-functionalized 1,6-diene, 1,6-diyne... 

Cyclopolymerizations of functionalized 1,6 dienes such as 4-trimethyl-silyoxy-1,6-heptadiene are also possible, with B(C6F5)3 as cocatalyst and bis-(pentamethylcyclopentadienyl)zirconocenes as catalysts. Hydrolysis of the product with HC1 gives polymethylene-3-hydroxycyclohexane. With the same catalyst, Kesti et al. (269) succeeded in polymerizing 5-/ /V-diisoprop-lyl-amino-l-pentene and 4-tert-butyldimethylsiloxy-l-pentene. 

Functionalized 1,6-dienes in the presence of stoichiometric amounts of triethylsilane undergo palladium-catalyzed cyclization-hydrosilylation to form (silyl)methyl-substituted cyclopentanes (195). l-Buten-3-ynes, in the presence of palladium monoferrocenylmonophosphine, or bis(ferrocenyl)monophosphine, undergo asymmetric 1,4-hydrosilylation with trichlorosilane to give axially... 

Reaction type 3 (equation 10), where the complete hetero-l,3-diene skeleton is incorporated into the newly formed ring system, occurs with compounds having both a nucleophilic center and an electrophilic center If these two functionalities are in positions 1 and 2, various types of six-membered ring systems become accessible 4,4-Bis(trifluoromethyl)-I,3-diaza-1,3-butadienes require only room temperature to react with acetyl cyanide to yield l,4,5,6-tetrahydropynmidin-6-ones [96] Likewise, certain open-chain 1,3-diketones (acetylacetone and acetoacetates) and the heterodiene form six-membered nng systems [97] (equation 19)... 

Substituted aminophenols and phenolic or anilino moieties bearing N-hetero-cycles contain two distinguished CB functional centres. Substituted BQMI 57 are formed via 4-aminophenoxyl after ROO trapping by aminophenols. For example, the aminophenolic moiety creates the active part of 2,4-bis(octylthio)-6-(3,5-di-ter -butyl-4-hydroxyanilino)-1,3,5-triazine, a very efficient AO for diene based polymers. The respective QI 173 is formed transiently and 2,6-di-fm-butyl-l, 4-benzoquinone is released by hydrolysis of 173 in the ultimate phase of its lifetime [251]. The respective QI are also formed in sacrificial transformations of 6-hydroxy- or 6-anilino-2,2,4-trimethyl-1,2-DHQ, 6- or 8-hydroxy-2,2,4-trimethyl-1,2,3,4-tetrahydroquinolines or 6-hydroxycarbazole [37]. All these bifimctional heterocyclic amines are strong AO. 

AMI semi-empirical and B3LYP/6-31G(d)/AMl density functional theory (DFT) computational studies were performed with the purpose of determining which variously substituted 1,3,4-oxadiazoles would participate in Diels-Alder reactions as dienes and under what conditions. Also, bond orders for 1,3,4-oxadiazole and its 2,5-diacetyl, 2,5-dimethyl, 2,5-di(trifluoromethyl), and 2,5-di(methoxycarbonyl) derivatives were calculated <1998JMT153>. The AMI method was also used to evaluate the electronic properties of 2,5-bis[5-(4,5,6,7-tetrahydrobenzo[A thien-2-yl)thien-2-yl]-l,3,4-oxadiazole 8. The experimentally determined redox potentials were compared with the calculated highest occupied molecular orbital/lowest unoccupied molecular orbital (HOMO/LUMO) energies. The performance of the available parameters from AMI was verified with other semi-empirical calculations (PM3, MNDO) as well as by ab initio methods <1998CEJ2211>. 

The reaction of 1,4-diphenylbuta-l,3-diene (2) with trithiazyl trichloride (3) yields a bi(thiadiazole) (4), an isothiazoloisothiazole (5), a dithiazolothiazine (6), and two thiazin-odithiatriazepines (7) and (8) by 1,2-, 1,3-, and 1,4-cycloaddition reactions (Scheme 2). The bridged-mode (/3-tether) tandem inter-[4 -E 2]/intra-[3 -E 2] cycloaddition of (ii)-2-methyl-2-nitrostyrene (9) with 1-butoxypenta-1,4-diene (10) produces stable tricyclic nitroso acetals (11) which afford, after reduction and protection, highly functionalized aminocyclopentanedimethanol triacetates (12) (Scheme 3). ... 

The catalytic asymmetric /-selective Diels-Alder annulation of a, -unsaturated /-butyrolactams with enones provided a synthesis of, y-functionalized bridged bi-or tri-cyclic dihydropyranopyrrolidin-2-ones in one step (up to 98% yield, >20 1 dr, and 99% ee) The inverse-electron-demand aza-Diels-Alder cycloaddition 0 of A-aryl-a,/0-unsaturated ketimines with enecarbamates in the presence of chiral bifunctional phosphoric acids produced 4,5,6-trisubstituted 1,4,5,6-tetrahydropyridines having three contiguous stereogenic centres in up to 84% yield, 95 5 dr, and 95% 5-Alkenylthiazoles react as in-out dienes with e-poor dienophiles in polar 44-2- 0 cycloaddition reactions. The cycloadditions are site selective. The mechanism is thought to lie between a concerted but highly asynchronous process and a stepwise process. 

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