Suzuki reactions donor-acceptor

Fluorene-di(thiophene)quinoxaline copolymers were synthesized through Suzuki reactions of a dibromo-di(thiophene)quinoxaline monomer (donor-acceptor-donor system) carrying various substituents on the quinoxaUne system, with a ftuorene diboronate, as shown in Scheme 21 [99]. 

Suzuki et al. reported the photochemical reaction of CT crystals, in which cycloaddition reaction of bis(l,2,5-thiadiazolo)tetracyano-quinodimethane 17 (electron acceptor) and 2-divinylstylene 18 (electron donor) is efficiently induced (Scheme 3). [17] A structural feature of the CT crystal is the asymmetric nature of the inclusion lattice because of the adoption of a chiral space group, P2. The [2 + 2] photoadduct 19 was formed via the single crystal-to-single crystal transformation, and the optically active product with 95% ee was obtained. 

Under the same conditions the sterically more demanding 2-chlorotoluene is coupled in 70% yield. However longer reaction times are necessary. Acceptor- as well as donor-substituents are tolerated under these conditions. Tri-tert.-butyl-phosphane is the ligand of choice in Suzuki-couplings [3] as well 2-chlorotoluene reacts with 2-methyl-phenylboronic acid to 2,2 -disubstituted biphenyl in 87% yield [eq. (b)]. 

The synthetic scheme of Suzuki et al. [59] was based on the fact that adducts resulting from furan addition often rearrange to phenols (compare with [61]). In our group, we also investigated the reactions of naphthoquinones with siloxy-furans such as 64. However, instead of the expected [4 + 2] cycloaddition, a Michael addition that proceeded without catalyst occurred in the reaction with 3-chlorojuglone (63) [39]. Interestingly, both the Michael acceptor 63 and the donor 64 reacted in a 1,4-reaction mode. The regio- and stereochemistry of the product 65 were confirmed by x-ray analysis (Scheme 18). 

Despite the inherent instability of 2-chloroindole, derivatives have found many synthetic applications. Eissenstat and colleagues prepared more than 140 cannabinoid mimetics 10 (Scheme 6, equation 1) [36]. Interestingly, longer reaction times for this chlorination led to trimer 11 (72%). Similarly, Hiyoshi synthesized the bromo trimer 12 [37], tetramer 13 [38], and alkenyl derivatives via Suzuki coupling as novel donor-x-acceptor molecules. Fang [39]... 

Lactobacillus, Leuconostoc and Bifidobacterium employ the PK pathway as the central fermentative pathway. PK catalyses the cleavage of a ketose phosphate (donor substrate such as o-xylulose 5-phosphate), utilizing an inorganic phosphate (acceptor substrate) to produce an aldose phosphate released from the donor (first product such as glyceraldehyde 3-phosphate), water (second product) and acetyl phosphate (third product) (Figure 4.3). The first half of the reaction of PK is identical to that of TK. However, the subsequent reaction catalysed by PK is distinct from TK (Yevenes and Frey 2008). PK releases a water molecule (dehydration) from the a,p-dihydroxyethyl ThDP intermediate to form the acetyl ThDP intermediate, and then a nucleophilic attack of the acceptor substrate (phosphate) on the acetyl ThDP intermediate yields the third product (acetyl phosphate). The crystal structures of the intermediates before and after the dehydration step have been reported (Suzuki et al. 2010). 

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