Enantioselective titanium-promoted 1,2-additions of carbon nucleophiles to carbonyl compounds
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Phosphine-catalyzed formation of carbon-sulfur bonds: catalytic asymmetric synthesis of gamma-thioesters.
A method for catalytic asymmetric gamma sulfenylation of carbonyl compounds has been developed. In the presence of an appropriate catalyst, thiols not only add to the gamma position of allenoates, overcoming their propensity to add to the beta position in the absence of a catalyst, but do so with very good enantioselectivity. Sulfur nucleophiles are now added to the three families of nucleophil...
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The 1,4-conjugate addition of nucleophiles to α,β-unsaturated carbonyl compounds represents one fundamental bond-forming reaction in organic synthesis. The development of effective organocatalysts for the enantioselective conjugate addition of malonate, nitroalkane and other carbon and heteroatom nucleophiles to cycloenones constitutes an important research field and has been explored in recent...
متن کاملEnantioselective addition of organozinc reagents to carbonyl compounds*
Different chiral camphorsulfonamide derivatives containing a hydroxy or a sulfonamido functionality, as well as chiral 1,2-hydroxysulfonamides, have been evaluated as chiral promoters in the classical enantioselective addition of dialkylzinc reagents to aldehydes in the presence of titanium tetraisopropoxide (ee up to 96 %). Surprisingly, ligands with a structure of isoborneol are able to promo...
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Conjugate addition (1,4-addition) of carbon nucleophiles to a; b-unsaturated compounds is one of the most important carbon–carbon bond-forming strategies in synthetic organic chemistry [1]. The versatility of the conjugate addition is mainly due to the large variety of nucleophiles (organometallic reagents, Michael donors, other carbanions) and acceptors (a; b-unsaturated aldehydes, ketones, ni...
متن کاملβ-Carbon activation of saturated carboxylic esters through N-heterocyclic carbene organocatalysis.
The activation of the α-carbons of carboxylic esters and related carbonyl compounds to generate enolate equivalents as nucleophiles is one of the most powerful strategies in organic synthesis. We reasoned that the horizons of chemical synthesis could be greatly expanded if the typically inert β-carbons of saturated esters could be used as nucleophiles. However, despite the rather significant fu...
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