A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

• Antonia Mielgo and
• Claudio Palomo

Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90

• therapeutical candidates because of their high lipophilicity and membrane permeability [44][51]. A major catalytic entry to α,α-disubstituted (quaternary) amino acids is the α-functionalization of an appropriate template as, for instance, an α-imino ester or lactone, followed by hydrolysis [49][52][53]; but

Synthesis of chiral N-phosphinyl α-imino esters and their application in asymmetric synthesis of α-amino esters by reduction

• Yiwen Xiong,
• Haibo Mei,
• Lingmin Wu,
• Jianlin Han,
• Yi Pan and
• Guigen Li

Beilstein J. Org. Chem. 2014, 10, 653–659, doi:10.3762/bjoc.10.57

• chromatography and recrystallization. The chiral phosphinyl auxiliary could be easily cleaved under acidic conditions. Keywords: α-amino ester; α-imino ester; group-assisted purification; phosphinyl auxiliary; reduction; Introduction α-Imino esters play a very important role in the field of imine chemistry [1

• phosphinyl amide 1 (Table 1). Common dehydrating reagents, like 4 Å molecular sieves and magnesium sulfate, resulted in no desired product neither at room temperature nor under reflux (Table 1, entries 1–4). Very poor chemical yields of α-imino ester 3a were detected when tetraethoxytitanium or

• conducted in the presence of TiCl4/Et3N at room temperature for 12 h (Table 1, entries 9–16). 31P NMR of the crude product predicted almost complete consumption of phosphinyl amide 1 but yields were very low. After careful study, we found that the obtained α-imino ester was not stable and decomposed slowly

N-Heterocyclic carbene-catalyzed direct cross-aza-benzoin reaction: Efficient synthesis of α-amino-β-keto esters

• Takuya Uno,
• Yusuke Kobayashi and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2012, 8, 1499–1504, doi:10.3762/bjoc.8.169

• with α-imino ester, catalyzed by N-heterocyclic carbene, leads chemoselectively to α-amino-β-keto esters in moderate to good yields with high atom efficiency. The reaction mechanism is discussed, and it is proposed that the α-amino-β-keto esters are formed under thermodynamic control. Keywords: α

• -amino-β-keto esters; cross-aza-benzoin; α-imino ester; N-heterocyclic carbenes; organocatalysis; umpolung reactions; Introduction α-Amino-β-keto ester derivatives are one of the fundamental structural subunits in natural products such as miuraenamides [1], and important building blocks for the

• mechanism, a 0.5 equiv of benzoin (6) was used instead of aldehyde 1a under standard conditions, affording the cross-coupled product 5a in 40% yield (Scheme 2). In addition, when the reaction was conducted with α-amino-β-keto ester 5b in place of α-imino ester 4, the cross-over product 5a was not detected