Diene complexes reaction with

I. Conjugated Diene Complexes Reaction with Metal Complexes. 

Another modification of the double silylation process reported by Tanaka and co-workers involves the use of a bis(hydrosilane) instead of a disilane as the reactant molecule.61 This reaction can be described as a dehydrogenative double silylation, in that two Si-H bonds are activated rather than an Si-Si bond. The system is best catalyzed by Pt(CH2=CH2)(PPh3)2 other Pt, Pd, Ru, and Rh complexes give only very low yields of the double-silylated products. Alkynes, alkenes, and dienes undergo reaction with the bis (hydrosilane) with a range of results. Silicon-oxygen bonds and silicon-nitrogen bonds can also be formed by this method and are discussed in the appropriate sections later. 

The scandium diene complex reacts with PhCN via initial nitrile insertion into the Sc-diene bond to give a dimeric r/2-imido species, but with a 2,2 -bipyridine under elimination of the free diene (Scheme 71). The latter reaction... 

Dienes, chelating reaction with metal atoms 5.S.2.5.3 Dienes, conjugated reaction with metal atoms 5.S.2.4.6 [-Dienyl complexes from organoaluminums 5.8.2.11.3 from organoborons 5.8.2.11.1 from organomercurials 5.8.2.11.2 from organotins 5.8.2.11.1... 

Vinyl- and 3-vinyl-thiophenes (618) and (619) behave as a diene on reaction with dienophiles to give six-membered ring fused thiophenes (Equations (112) and (113)). The reaction generally gives a complex mixture as exemplified by reactions of (618) and (619) with DMAD <85T2435,87T269,... 

Although reaction of MeQ- with [( 6 Cyclohexadienyl)Fe(CO)3]+ yields only the [r -5-cA o-cyclohexa-l,3-diene)Fe(CO)3 complex, reaction with MeOH yields both the exo- and e kinetic product of this reaction, its formation is reversible in the presence of acid or MeOH. ... 

The mechanism by which Lewis-acids can be expected to affect the rate of the Diels-Alder reaction in water is depicted in Scheme 2.6. The first step in the cycle comprises rapid and reversible coordination of the Lewis-acid to the dienophile, leading to a complex in which the dienophile is activated for reaction with the diene. After the irreversible Diels-Alder reaction, the product has to dissociate from the Lewis-acid in order to make the catalyst available for another cycle. The overall... 

I.l.IJ Reactions nitlr 1,2-, 1.3-. ami 1.4-dienes. The reaction of conjugated dienes with aryl and alkenyl halides can be explained by the following mechanism. Insertion of a conjugated 1.3-diene into an aryl or alkenylpalladium bond gives the T-allvlpalladium complex 243 as an intermediate, which reacts further... 

Yamamoto et al. were probably the first to report that chiral aluminum(III) catalysts are effective in the cycloaddition reactions of aldehydes [11]. The use of chiral BINOL-AlMe complexes (R)-S was found to be highly effective in the cycloaddition reaction of a variety of aldehydes with activated Danishefsky-type dienes. The reaction of benzaldehyde la with Danishefsky s diene 2a and traws-l-methoxy-2-methyl-3-(trimethylsilyloxy)-l,3-pentadiene 2b affords cis dihydropyrones, cis-3, as the major product in high yield with up to 97% ee (Scheme 4.6). The choice of the bulky triarylsilyl moiety in catalyst (J )-8b is crucial for high yield and the en-antioselectivity of the reaction in contrast with this the catalysts derived from AlMe3 and (J )-3,3 -disubstituted binaphthol (substituent = H, Me, Ph) were effective in stoichiometric amounts only and were less satisfactory with regard to reactivity and enantioselectivity. 

The mechanism of the cycloaddition reaction of benzaldehyde 2a with Danishefsky s diene 3a catalyzed by aluminum complexes has been investigated theoretically using semi-empirical calculations [14]. It was found that the reaction proceeds as a step-wise cycloaddition reaction with the first step being a nucleophilic-like attack of Danishefsky s diene 2a on the coordinated carbonyl compound leading to an aldol-like intermediate which is stabilized by interaction of the cation with the oxygen atom of the Lewis acid. The next step is the ring-closure step, giving the cycloaddition product. 

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