Search results for "DMPU"
showing 2 items of 2 documents
Cyclic ureas (DMI, DMPU) as efficient, sustainable ligands in iron-catalyzed C(sp2)–C(sp3) coupling of aryl chlorides and tosylates
2017
Iron-catalyzed cross-coupling has emerged as a powerful tool for sustainable catalysis. However, by far the most common ligand in iron-catalyzed cross-couplings for preparative and industrial applications is reprotoxic NMP. Herein, we report that cyclic ureas (DMI, DMPU) are efficient and sustainable alternatives to NMP in iron-catalyzed alkylations of aryl chlorides and tosylates with alkyl Grignard reagents. This environmentally benign method accomplishes traditionally challenging C(sp2)–C(sp3) cross-coupling with organometallics possessing β-hydrogens with efficiency matching or superseding NMP. The reaction is compatible with a variety of electrophilic functional handles. Applications t…
Stereoselective Synthesis of γ-Fluorinated α-Amino Acids Using 2-Hydroxy-3-pinanone as an Auxiliary
2000
(+)-(S)-2-Amino-4-fluorobutanoic acid (5a) (> 96% ee), its α-methylated derivative (+)-(S)-5b (85% ee), and (−)-(S)-2-amino-4-fluoro-4-pentenoic acid (10) (81% ee) were synthesized by diastereoselective alkylation in the presence of LDA at low temperatures. Alkylation of (+)-(R,R,R)-2-hydroxy-3-pinanone based imines of glycine tert-butyl ester 1a or alanine isopropyl ester 1b with 1-bromo-2-fluoroethane (2) or 3-bromo-2-fluoropropene (7), respectively, followed by stepwise deprotection was used. The selectivity of the alkylation increased by lithium/magnesium exchange or for 1b also by addition of DMPU. Differences in the reactivity of enolate alkylations of enantiomerically pure or racemic…