72658-17-4

Upstream product

• 1113-75-3 N,N-diisopropylpropionamide 
• 100-52-7 benzaldehyde 

Relevant academic research and scientific papers

Enolboration. 7. Dicyclohexyliodoborane, a Highly Stereoselective Reagent for the Enolboration of Tertiary Amides. Effects of Solvent and Aldolization Temperature on Stereochemistry in Achieving the Stereoselective Synthesis of either Syn or Anti Aldols

A highly stereoselective enolboration of tertiary amides has been accomplished for the first time with dicyclohexyliodoborane, Chx2BI.A systematic study of the enolboration of representative N,N-dialkylpropionamides (CH3CH2CONR'2) with Chx2BI in the presence of various tertiary amines of variable steric requirements revealed an unusual aldol stereoselectivity in different solvents and at different aldolization temperatures.Both the nature of solvent and the aldolization temperature influence the stereochemistry of enolboration, with the solvent effect being greater than that of the temperature.Aliphatic and alicyclic hydrocarbon solvents favor formation of the syn aldols from the enol borinates by aldolization at lower temperature (-78 deg C), whereas most of the other solvents examined, such as aromatic and chlorinated aliphatic solvents, favor formation of the anti aldols by aldolization at relatively higher temperatures (0 or 25 deg C).The remarkable effects of both temperature and solvent in the case of tertiary amides raise a question about the validity of the previously assumed constancy of the Z to syn and E to anti relationship, suggesting either a possible isomerization of enol borinates with temperature or a different aldolization transition state with different solvent.While the effect of stric requirements of the dialkylamino group of the tertiary amide does not contribute significantly to the stereochemistry, that of the amine exerts a considerable influence.The present study establishes a simple procedure for the stereoselective synthesis of either syn or anti aldols from representative tertiary amides merely by changing the solvent and the aldolization temperature.

Acyclic Stereoselection. 7. Stereoselective Synthesis of 2-Alkyl-3-hydroxy Carbonyl Compounds by Aldol Condensation

The stereochemistry of the aldol condensation of preformed lithium enolates of a variety of ethyl ketones and propionic acid derivatives with aldehydes has been investigated.It is found that certain compounds give completely or nearly completely one diastereomeric enolate and that the stereostructure of the resulting aldol is correlated with the stereostructure of the enolate from which is formed.The observed stereochemistry may be understood in terms of an ordered transition state in which both oxygens are oriented in more or less the same direction.It is shown that the observed stereochemistry is kinetically controlled.In many cases, the initial aldol adduct equilibrates to furnish predominantly a threo isomer.The rate of equilibration varies widely, ranging from very fast at -60 deg C with the propiophenone-benzaldehyde adduct to slow at 25 deg C for the ethyl tert-butyl ketone-benzaldehyde adduct.The equilibration behavior of lithium ketolates is compared with that of zinc ketolates, and some differences are noted.A method for achieving erythro-threo equilibration via a chloral hemiacetal is presented.A new reagent is introduced (trimethylsilyloxy ketone 36) which may be used to stereoselectively homologate an aldehyde to an erythro α-methyl-β-hydroxy acid.As an application of the use of stereoselective aldol condensations in synthesis, (+/-)-ephedrine (48) has been synthesized from benzaldehyde in 71 percent overall yield.

ALDOL DIASTEREOSELECTION VIA ZIRCONIUM ENOLATES. PRODUCT-SELECTIVE, ENOLATE STRUCTURE INDEPENDENT CONDENSATIONS.

Both (E)- and (Z)-zirconium enolates have been shown to undergo selective kinetic aldol condensation to give mainly erythro-β-hydroxy ketones, esters and amides.