1.3- Dienes aryl-substituted

The copper-catalyzed additions of sulfonyl chlorides to conjugated dienes and trienes73 as well as to aryl-substituted cyclic olefins74 and substituted styrenes have been described75 for example, arenesulfonyl chlorides add to vinylarenes providing good to excellent yields75 of /J-chlorosulfones ... 

Aryl group substituted butatrienes and hexapentaenes can be selectively reduced with Zn-ZnCl2-H20 to result in aryl-substituted 1,3-butadienes and hexa-l,5-dien-3-ynes, respectively (equations 191 and 192)315. 

Isomerization of 1,3-dienes (12, 36).3 The 1,5-hydrogen shift in isomerization of 1,3-dienes catalyzed by (naphthalene)Cr(CO)3 (1) can be used for synthesis of aryl-substituted exocyclic alkenes, which are not readily available by coupling of aryl halides with exocyclic vinyl halides. 

The main types of substrates investigated so far are polycyclic aromatic compounds, aryl substituted carbo- and heterocyclic pentadienes, cyclic 1,3-dienes, furans, and olefins. It has turned out that type II photooxygenation of these compounds in solution occurs via the oxygen-activation mechanism. 

The scope and limitations of the Lewis acid-catalyzed additions of alkyl chlorides to carbon-carbon double bonds were studied.51 Since Lewis acid systems are well-known initiators in carbocationic polymerizations of alkenes, the question arises as to what factors govern the two transformations. The prediction was that alkylation products are expected if the starting halides dissociate more rapidly than the addition products.55 In other words, addition is expected if the initial carbocation is better stabilized than the one formed from the dissociation of the addition product. This has been verified for the alkylation of a range of alkyl-and aryl-substituted alkenes and dienes with alkyl and aralkyl halides. Steric effects, however, must also be taken into account in certain cases, such as in the reactions of trityl chloride.51... 

All types of olefins can serve as substrates. Suitable acyclic olefins include ethylene, terminal and internal monoenes up to and including tetrasubstituted-double bonds, and aryl-substituted olefins. With dienes (and polyenes) an additional, intramolecular reaction pathway becomes available which leads to cyclic olefins (Reaction 2). 

As noted, these zinc reagents find extensive application in the preparation of fluorinated styrenes [113,114], aryl-substituted fluorinated propenes [114], fluorinated dienes [115,116], and trifluorovinyl ketones [117], as illustrated in equations 83-88... 

As expected from the results obtained in the arylation of dienes with secondary amines (Section 4.4.5.l.2.iii), the amine attacks the least-substituted (hindered) end of the ir-allylic group. An exception to this behavior occurs in these reactions as it did in the diene arylation case where there are two methyl substituents on one terminal allylic carbon, in which case the amine attacks this tertiary carbon (equation 34).s7 If groups larger than methyls are present on one terminal allylic carbon, steric hindrance to attack at that carbon causes reaction at the other end of the allyl system. 

The 5,7-diaryl-2-fluoro-4/7-l,3-diazepines have been synthesized from 3-aryl-substituted 277-azirines and difluoro-carbene (Scheme 13). The reaction involves isomerization of azirinium ylide into a 2-aza-l,3-diene, which undergoes [4+2] cycloaddition with the starting azirine, followed by ring expansion and dehydrofluorination <2006TL639>. 

This palladium-catalyzed three-component coupling reaction leading to the formation of aryl-substituted allylic amines was recently adapted to solid-phase synthesis (Scheme 8.23). Amines were chosen to attach to a solid support (Rink resin) in this three-component coupling process and were reacted with a variety of aryl halides and linear or cyclic non-conjugated dienes, the reaction being carried out at 100 °C for two days in the presence of palladium acetate and diisopropylethyl-amine. A wide variety of aryl-substituted allylic amines were then obtained after cleavage from the solid support by trifluoroacetic acid [60],... 

Alkyl- or aryl-substituted pyrazole 1-oxides 94 can be obtained in acceptable yields by oxidative cyclization of O-silylated 3-oximimines like 1 -tert-hutyldimethyIsilyloxy-4-methylamino-1 -azab nta-1,3-diene 93 using copper(II) sulfate as the oxidant and pyridine and acetonitrile as the solvent. The oximimines are prepared from 1,3-dicarbonyl compounds 92 in a one-pot process. The method also gives access to 2-alkyl and aryl-pyrazole 1-oxides R=H devoid of substituents at the ring carbon atoms (94 Ri = R2=H) (1995JCS(P1)2773) (Scheme 27). 

Treatment of aryl-substituted bis(iV,iV-dimethylcarbamoylseleno)methanes 168 with stannic chloride provides a convenient room temperature method for the generation of selenals which can be trapped by dienes (Equation 69) <2005TL3775>. 

Super Hydride is one of the most powerful nucleophilic reducing agents available, capable of reducing many functional groups. It is also highly selective. The exocyclic double bond in aryl-substituted fulvenes has an increased polarity, due to the inductive effects of their respective aryl groups. This increased polarity allows for selective nucleophilic attack at this double bond and not at the diene component of the fulvenes. Other examples of the nucleophilic addition of hydrides to substituted fulvenes (albeit with alkyl or unsubstituted phenyl group functionality)... 

Alkenes without allylic H atoms—such as ethylene, acceptor-substituted ethylenes, and styrene—can be alkenylated and arylated by Heck reactions in a clearly predictable fashion. These alkenes can be alkenylated to provide 1,3-dienes, a,/3,y,S-unsaturated carbonyl compounds (Figures 13.27 and 13.28), a,j8,y,8-unsaturated carboxyl compounds (Figures 13.27 and 13.28), as well as aryl-substituted 1,3-dienes. Moreover, the same alkenes can be arylated to give styrenes, a./l-unsaturated /3-arylated carbonyl compounds, or a./l-unsaturated /3-arylated carboxyl compounds (Figure 13.26) and stilbenes (Figure 13.29). 

Konovalov et found the reaction between 138 and several aryl-substituted styrenes to be of the diene-donor, dienophile-acceptor type they also investigated the kinetics and heats of the reaction between 138 and cyanoethylenes, maleic anhydride, and aryl substituted N-arylmalei-... 

Indene can participate as the cne component in [4 + 2] and [2 + 2] cycloaddition reactions with diazene dicarboxylates and triazolediones. Aryl-substituted alkenes, however, can participate as the diene components in cycloaddition reactions with the same diazene compounds, although the reaction can follow different pathways depending on the nature of the substituents on the vinyl and phenyl groups. 

Acyl isocyanates are more reactive than alkyl or aryl isocyanates. However, the presence of an additional rr-bond conjugated to the C>i-N bond of the isocyanate opens the possibility for [4 + 2] cycloadditions to compete with normal [2 + 2] additions. Reactions with alkyl and aryl substituted alkenes are rather slow. Propene, tranj-2-butene, styrene and conjugated dienes give only 3-lactams, albeit in moderate yields (Scheme 25). The strained double bond of norbomene, a reactive dienophile, adds across the conjugated 4iT-system of trichloroacetyl isocyanate (equation 51). 

Diels-Alder cycloadditions of carbonyl compounds with aldehydes and ketones provide a powerful method for synthesis of 5,6-dihydropyrans, which are useful synthons for a variety of purposes. This methodology was slow to develop since early work indicated that simple carbonyl compounds react poorly with most alkyl and aryl substituted 1,3-dienes. However, with the understanding that [4 + 2] cycloadditions are facilitated by Lewis acid catalysts and high pressure, along with the recent availability of highly reactive oxygenated dienes, this chemistry has been increasingly exploited in total synthesis. 

Cycloadditions of ketenes with alkenes and alkynes constitute the most popular method for the synthesis of cyclobutanones and cyclobutenones. Unfoitunately, however, this process is truly general only for highly nucleophilic ketenophiles such as conjugated dienes and enol ethers. In general, unactivated alkenes and alkynes fail to react in good yield with either alkyl- or aryl-substituted ketenes, or with ketene itself To circumvent this limitation, dichloroketene is usually employed as a ketene equivalent, since this electrophilic ketene reacts well with many types of unactivated multiple bonds, and the resultant cycloadducts undergo facile dechlorination under mild conditions. ... 

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