Asymmetric domino reactions by Helene Pellissier, James Spivey

Chemical Engineering

By Helene Pellissier, James Spivey

This ebook covers the newest advancements in uneven domino reactions, focussing on these released within the final 6 years. those attention-grabbing reactions have quickly turn into essentially the most present fields in natural chemistry, when you consider that they enable achieving simply excessive molecular complexity in an economically beneficial approach with merits of discount rates in solvent, time, strength, and prices. Unsurprisingly, the excessive degrees of potency and enantioselectivity as a rule reached in those reactions were exploited for the construction of a large variety of complicated chiral molecules with dense stereochemistry and performance, that are motifs found in biologically lively compounds and typical items. The e-book is split into 3 valuable sections, dealing successively with uneven domino reactions in accordance with using chiral auxiliaries, uneven domino reactions in accordance with using chiral steel catalysts, and uneven domino reactions in line with using chiral organocatalysts, protecting the literature because the starting of 2006.

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This carbocation can be formed by elimination, or by addition of a positive particle such as a proton. The carbocation then reacts with a nucleophile to form a new carbocation that undergoes one or more comparable further transformations in a cationic–cationic process, finally being trapped by a nucleophile or stabilised by elimination of a proton. As an example, a diastereoselective cationic domino cyclisation was employed by Blaauw et al. 33, treatment of various enantiopure dipeptides by a catalytic amount of 4-toluenesulfonyl (Ts)OH underwent the formation of the corresponding bicyclic N,N-acetals through cascade cationic cyclisations in good yields and diastereoselectivities of up to 88% de in favour of the transisomer.

This chiral domino product was further converted into zaragozic acids A and C. 67 Later, Schaus et al. 68 The process evolved through the in situ formation of dipole 31 by treatment of substrate with rhodium(II) acetate dimer in refluxed benzene. 44). 43 Rh-catalysed domino carbonyl ylide formation–1,3-dipolar cycloaddition reaction of a di-tert-butyl D-tartrate-derived diazo ester with 3-butyn-2-one. 44 Rh-catalysed domino carbonyl ylide formation–1,3-dipolar cycloaddition reaction of a chiral dihydropyrimidone diazo ester with a maleimide.

27 This domino process provided the corresponding enantiomerically enriched functionalised cyclohexa-1,3-diene derivatives in moderate to good yields and enantioselectivities (25–90% ee) when using (R)-2-MeO-MeOBIPHEP-derived phosphonium salt as chiral auxiliary. 16, the chiral phosphonium salt generated the corresponding chiral phosphorus ylide 13, which underwent Michael addition to the a,b-unsaturated enone to give an enolate 14. This enolate generated a novel phosphorus ylide 15 which underwent intramolecular Wittig olefination to give the final cyclohexadiene.

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