Enantioselective Conjugate Addition of a Lithium Ester Enolate Catalyzed by Chiral Lithium Amides

Access to Anti or Syn 2-Amino-1,3-diol Scaffolds from a Common Decarboxylative Aldol Adduct

A straightforward synthetic pathway allowing the access to anti or syn 2-amino-1,3-diol scaffolds is presented. The strategy relies on a diastereoselective organocatalyzed decarboxylative aldol reaction of a N-Boc-hemimalonate that is easily formed from commercial N-Boc-diethyl malonate. Although this method has been optimized previously with the N-Bz-hemimalonate analogue, this key step was reinvestigated with the N-Boc derivative to improve the required reaction time, the yield, and the diastereoselectivity. The new conditions enhance this transformation, and quantitative yields and anti/syn ratios up to 96:4 can be obtained. The anti aldol product was easily isolated in pure form and then taken forward as the key precursor in the preparation of both a set of ten N-/O-alkylated anti 2-amino-1,3-diol derivatives and the syn congeners.

Chiral Lithium Amides: Tuning Asymmetric Synthesis on the Basis of Structural Parameters

An overview on the structural arrangements adopted by Chiral Lithium Amides (CLAs), alone or in mixed complexes, is presented. These species are important reagents for asymmetric synthesis and understanding their organization is essential to improve their design and the reaction conditions.

Catalytic asymmetric direct-type 1,4-addition reactions of simple esters

Catalytic asymmetric 1,4-addition reactions of simple esters have been developed. The desired reactions proceeded smoothly with high enantioselectivities.

Probing solvent effects on mixed aggregates associating a chiral lithium amide and n-BuLi by NMR: from structure to reactivity

An NMR study of a 1 : 1 mixture of a chiral lithium amide (4a) and n-BuLi shows that depending on the solvent employed (Et2O or THF) a mixed aggregate can form in proportions that are directly related to the ees measured during the enantioselective alkylation of o-tolualdehyde by these same species.

Direct enantioselective conjugate addition of carboxylic acids with chiral lithium amides as traceless auxiliaries

Michael addition is a premier synthetic method for carbon-carbon and carbon-heteroatom bond formation. Using chiral dilithium amides as traceless auxiliaries, we report the direct enantioselective Michael addition of carboxylic acids. A free carboxyl group in the product provides versatility for further functionalization, and the chiral reagent can be readily recovered by extraction with aqueous acid. The method has been applied in the enantioselective total synthesis of the purported structure of pulveraven B.

Amino Oxazolines as Easily Accessible Water Stable Ligands for Palladium Catalysed Aqueous Heck Reaction

A series of amino oxazolinyl ligands were screened for palladium catalysed Heck reaction. These ligands work well as phosphine free system in aqueous, micellar medium, can be effectively recovered and reused for subsequent cycles.

Hydroxyl group-directed organocatalytic asymmetric Michael addition of alpha,beta-unsaturated ketones with alkenylboronic acids

The organocatalytic asymmetric Michael addition of organoboronic acids to gamma-hydroxy enones in the presence of an iminophenol-type thiourea catalyst is demonstrated. The hydroxyl group in the substrates plays a critical role in this reaction.

An efficient synthesis of gamma-amino acids and attempts to drive its enantioselectivity

Addition of carboxylic acid dianions to bromoacetonitrile lead, in good yields,to the corresponding gamma-cyanoacids, which on hydrogenation yielded gamma-amino acids. This two step methodology improves upon previously described results. Poor e.e's resultedfrom our attempts to drive the enantioselectivity of this transformation by chiral amide induction.