157239-25-3

Upstream product

• 179996-99-7 (2S,3R)-3-(tert-Butyl-dimethyl-silanyloxy)-2-[(R)-(4-methoxy-phenylamino)-phenyl-methyl]-butyric acid methyl ester 
• 783-08-4 [4-(benzylideneamino)phenyl]methanol 
• 179997-05-8 (2S,3R)-3-(tert-Butyl-dimethyl-silanyloxy)-2-[(R)-(4-methoxy-phenylamino)-phenyl-methyl]-butyric acid 
• 141781-29-5 S-2-Pyridyl (R)-3-tert-butyldimethylsilyloxybutanoate 

Relevant academic research and scientific papers

A catalytic amount of titanium tetrahalide as promoter for the addition reaction of silyl ketene acetals to imines

In the presence of a catalytic amount of TiBr4 or Til4, the reaction of silyl ketene acetals with imines smoothly proceeds to give the corresponding β-amino esters in high yield with high anti-selectivity.

Synthesis of β-lactams by condensation of the tin enolates of 2-pyridylthioesters with imines. A comparison between titanium and tin enolates

Addition of triethylamine to a mixture of 2-pyridylthioesters and SnCl4 or SnBr4 affords the corresponding tin(IV) enolates that add to imines to give β-lactams in fair to good yields and with various degree of trans/cis stereoselectivity. Examples of highly diastereofacially selective reactions carried out on a chiral thioester and on a chiral imine are also reported. The results are compared with those obtained in the condensations promoted by TiCl4 and TiBr4.

Synthesis of β-lactams by condensation of titanium enolates of 2-pyridylthioesters with imines. Influence of the imine structure on the trans/cis stereoselectivity

The condensation of the titanium enolates of C-2 alkyl substituted 2-pyridylthioesters with imines affords β-lactams in trans/cis ratios that largely depend on the structure of the C-imine residue. Bulky and non-chelating heteroatom-containing groups lead to the formation of trans β-lactams, while sterically non-requiring or chelating groups favour the formation of the cis-products. On the basis of NMR evidences a rationale is proposed to account for the observed stereoselectivity.