Dienyl acetal

Trichogramma evanescens Plodia interpunctella Ephestia spp. Host sex pheromone component [attraction, arrestment] (9Z, 12E) - Te tr ade ca- 9,12- dienyl acetate 28 [64]... 

In contrast with all the other species of Crematogaster studied till now, the venom of C. sp. 2 from Papua New Guinea did not contain mixtures of homologous compounds. Two derivatives, 136 and 137, characterized by the presence of a conjugated triene on one end of the chain, and by a 1,3-hydroxyketone at the other end, were isolated from this species (Fig. 23). These structures could constitute biosynthetic intermediates en route to the cross-conjugated dienone system. The venom of C. sp. 3 contained 4-oxo-2,5-dienyl acetates similar to... 

Stereoselective substitution reactions of chiral dienyl electrophiles have also been carried out. In analogy to the copper-promoted 8 2 reactions of simple allylic electrophiles [3], the corresponding 8 2 (1,3) substitutions of dienyl carbonates [43] have been reported to proceed with high anti selectivity. Interestingly, treatment of chiral dienyl acetal 63 with the Yamamoto reagent PhCu BFs gave rise to the formation of a 1 3 mixture of the anti-S l substitution product 64 and the syn-Sn2" (1,5) substitution product 65 (Eq. 4.28) [44]. A mechanistic explanation of this puzzling result has yet to be put forward, however. 

The effect of the nature of ion pairs as nucleophiles in a metal-catalysed substitution reaction has been investigated by determining product ratios for the Pd-catalysed allylic alkylations of substrates (9)-(ll) under various conditions, particularly with respect to catalyst ligands, nucleophiles, and counterions. Each dienyl acetate ionizes to form initially the vinyl (7r-allyl)-Pd intermediate corresponding most closely to the leaving group, i.e. (12) from (9), (13) from (11), but (12) and (13) from (10). The initial intermediate can then either be trapped by the nucleophile or it can begin to equilibrate to some mixture of vinyl 7r-allyl intermediates. If nucleophilic addition occurs before full equilibration, the product ratio is different for each substrate if... 

By application of the corresponding dienyl acetals 479 (n-BuLi and 0.1 equiv. of 11), enantioenriched fraw5-l-alkenyl-2-alkylcyclopropanes 481 are formed by 1,3-cycloelimination of the ally lie intermediate 480 (equation 131) . ... 

Numerous Amaryllidaceae alkaloids include phenanthridine skeletons, one of whose constructive methods constitutes an IEDA strategy. In some cases, the functionality on the dienophile influences the stereochemistry of cyclo addition reactions under high-pressure conditions. For example, the reactions of ( )-buta-l,3-dienyl acetate (6) and the quinolin-2(lH)-ones 7 gave rise to different configurations in the products 8 and 9, depending on the functional groups at the 4-position of 7 (Scheme 3). These results reflect... 

Scheme 3 Reactions of (E)-buta-l,3-dienyl acetate (6) with 2(lH)-quinolones 7 [25]...

When a deuterium-labelled bicyclic dienyl acetate reacted with a palladium catalyst using a PPh3 ligand, the major product formed by an. S n2 reaction. However, when the reaction was carried out using a DPPP or DPPB ligand, the major product was formed by an SN2 reaction.98 Both reactions gave predominantly the d.v-isomcr (Scheme 13). 

Interestingly, these authors53 and later others54 showed the importance of the silver counterion in such rearrangements. While silver tetrafluoroborate or silver nitrate gave the [3,3]-sigmatropic shift product mainly or exclusively, silver trifluoroacetate yielded the dienyl acetate through isomerization from the allenic ester (Scheme 3.33). 

Katsumata and colleagues disclosed electrochemically mediated vitamin B12-catalyzed tandem radical cyclizations (Fig. 68, entryl6) [329]. Bromoacetaldehyde dienyl acetal 288 reacted in a 5-exo/5-exo cyclization sequence applying electrochemically reduced vitamin B12 247 as the catalyst. Ester 289 was isolated in 65% yield as a mixture of four diastereomers after oxidation of the lactol. 

Katsumata and colleagues reported the first electrochemically mediated Ni(I)-catalyzed tandem radical cyclization reactions [139]. A bromoacetaldehyde dienyl acetal or the corresponding enynyl acetal underwent tandem 5-exo/5-exo cyclization reactions in the presence of Ni(cyclam) complex 98a under electrochemical reductive conditions (see Part 2, Sect. 5.3.3, Fig. 68). Bicyclic esters were isolated in 35% and 72% yields as a mixture of two and four diastereomers, respectively. 

Dodeca-7,9-dienyl Acetate (Pheromone) Hs /(CH2)6OCOCH3 ch3ch2 c=c C-C H / H H... 

The extent of pheromone degradation under field conditions was investigated with a microencapsulated formulation containing a saturated hydrocarbon and acetate (octadecane and tetradecyl acetate (14 Ac)), the corresponding monounsaturated hydrocarbon and acetate ((Z)-4-octadecene and (Z)-9-tetradecenyl acetate (Z9-14 Ac)) and a diunsaturated acetate ((Z,S )-9,ll-tetradeca-dienyl acetate (ZE9,ll-14 Ac)), chosen so that all the components had similar volatilities. On exposure to sunlight, loss of the diene was more rapid than loss of the monounsaturated components which in turn disappeared faster than the saturated components (Fig. 1). All components disappeared at a similar, slower rate when shielded from direct sunlight. 

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