β-Lactams as Formal Dipoles through Amide-Bond Activation
作者:Vincent Barbier、Jérôme Marrot、François Couty、Olivier R. P. David
DOI:10.1002/ejoc.201501342
日期:2016.1
Activation of β-lactams can be achieved by simple Lewis-base catalysis to trigger an unprecedented reaction based on the formal dipolar behaviour of a strained amide bond. A new synthetic route for 1,3-oxazinan-6-ones is presented by reaction of β-lactams with ethylglyoxylate, which after methodological optimizations identified 4-pyrrolidinopyridine as the catalyst of choice in aprotic polar solvents
The reaction of 1-acyl-3,5-dimethylpyrazoles 1 with CN compounds was kinetically controlled with syn stereoselectivity through a lithium enolate intermediate using lithium diisopropylamide. In contrast, the anti stereoselective reaction of 1 was caused by the action of diisopropylethylamine in the presence of magnesiumbromide under the thermodynamic control. Reaction of 2-acyl-3-phenyl-l-menthopyrazoles
Vinylaluminum Addition to Sulfinimines (<i>N</i>-Sulfinyl Imines). Asymmetric Synthesis of <i>anti</i>-α-Alkyl β-Amino Esters
作者:Franklin A. Davis、Hui Qiu、Minsoo Song、Narendra V. Gaddiraju
DOI:10.1021/jo9001504
日期:2009.4.3
Addition of vinylaluminum NMO reagents to N-(p-toluenesufinyl)- and N-(2-methypropanesulfinyl)-derived sulfinimines gives N-sulfinyl aza-Morita-Baylis-Hillman products (dr = 7:1 to 12:1) that result from addition of the reagent from the least hindered direction. Hydrogenation of the aza-MBH adducts with a Rh(I) catalyst affords anti-alpha-substituted N-sulfinyl-beta-amino esters in good yield and high dr (10:1 to 21:1).
Addition to activated imines of enolates from chiral N-acyloxazolidinones
作者:Isaac Abrahams、Majid Motevalli、Andrew J. Robinson、Peter B. Wyatt
DOI:10.1016/s0040-4020(01)89406-0
日期:1994.1
structure determination on 9a. The use of the lithium enolate of 1a at −78 °C gave only a 1.4:1 ratio of anti product 3a to syn product 4a, but this ratio was improved to >5: 1 by the use of the chlorotitanium enolate of 1a at −55 °C or below. Similar results were obtained by using the chlorotitanium enolate of 1b, but for the chlorotitanium enolate of the N (phenylacetyl)oxazolidinone 1c the proportion