intermolecular hydroacylation reaction of alkenes with simple aldehydes has been developed. This reaction offers a new approach to the selective preparation of branched ketones in high yields (up to 99%) and branched selectivities (up to 99:1). Experimental data provide evidence for reversible formation of acyl-nickel-alkyl intermediate, and DFT calculations show that the aldehydeC-H bond transfer
β-Hydroxy amides with stereodefined geometry represent an important unit present in various natural products. The diastereoselective preparation of amides carrying a secondary or tertiary alcohol in β-position is described here.
Stereoselective allylation of 2-formyl amides or 3-oxo amides has been studied. Treatment of 2-formyl-N,N-dimethylpropanamide (1a) with allylzinc bromide gave 3-hydroxy-2,N,N-trimethyl-5-pentenamide as a stereoisomeric mixture (2a : 3a = 63 : 37). Meantime, the reaction of 1a with allyltrimethylsilane in the presence of Lewis acid such as EtAlCl2 or BF3·OEt2 afforded threo-adduct 2a exclusively. Whereas treatment of 2-benzoyl-N,N-dimethylpropanamide (PhCOCH(Me)CONMe2) with allylzinc bromide provided erythro-3-hydroxy-2-methyl-3-phenyl-5-hexenamide with high stereoselectivity, allylation with allylsilane in the presence of a catalytic amount of n-Bu4NF afforded stereoisomeric threo hydroxy amide exclusively.
Highly stereoselective titanium-mediated addition of organocerium reagents to β-keto amides: an efficient synthesis of stereodefined β-hydroxy amides having a tertiary alcoholic fragment
A highlyefficient and stereoselective protocol for the TiCl4-mediated addition of organocerium reagents to β-keto amides is now available. The method allows the introduction of a large variety of carbon frameworks, including primary, secondary and tertiary alkyl chains, as well as aromatic, alkynylic and benzylic moieties, in high yields and with high stereoselection.
A Mn‐catalyzed diastereo‐ and enantioselective hydrogenation of α‐substituted β‐ketoamides has been realized for the first time under dynamic kinetic resolution conditions. anti‐α‐Substituted β‐hydroxy amides, which are useful building blocks for the synthesis of bioactive molecules and chiral drugs, were prepared in high yields with excellent selectivity (up to >99 % dr and >99 % ee) and unprecedentedly