(2R,3R)-3-[(1R)-1-{[tert-Butyl(dimethyl)silyl]oxy}ethyl]-4-oxoazetidin-2-yl Acetate in Zinc- and Samarium-Promoted Substitution Reactions with Methyl 2-Bromopropanoate and Methyl (2-Bromomethyl)prop-2-enoate. Unusual Cleavage of the N1‒C4 Bond in Azetidin-2-one Derivative with Migration of Methoxycarbonyl Group in Synthetic Approaches to Carbapenems and Their Analogs

• Published in: Russian journal of organic chemistry Vol. 54; no. 7; pp. 1023 - 1030
• Main Authors: Valiullina, Z. R., Khasanova, L. S., Selezneva, N. K., Spirikhin, L. V., Belokon’, Yu. N., Miftakhov, M. S.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 2018; Springer Nature B.V
• Subjects: Acetates; Alkylation; Catalysis; Chemistry; Chemistry and Materials Science; Cleavage; Dichloromethane; Iodine; Migration; Organic Chemistry; Reagents; Samarium; Substitution reactions; Zinc
• ISSN: 1070-4280; 1608-3393
• DOI: 10.1134/S1070428018070096

The use of zinc in Barbier-type reactions of (2 R ,3 R )-3-[(1 R )-1-{[ tert -butyl(dimethyl)silyl]oxy}-ethyl]-4-oxoazetidin-2-yl acetates with halogen derivatives led to the formation of expected substitution products. The reaction of the title compound with a reagent prepared from samarium powder, a catalytic amount of iodine, and methyl 2-bromopropanoate in THF gave an anomalous substitution product, methyl 2-{(2 S ,3 S )-3-[(1 R )-1-{[ tert -butyl(dimethyl)silyl]oxy}ethyl]-4-oxoazetidin-2-yl}-2( R , S )-methyl-3-oxopentanoate. Alkylation of the latter with methyl bromoacetate afforded methyl 2-{(2 S ,3 S )-3-[(1 R )-1-{[ tert -butyl(dimethyl) silyl]oxy}ethyl]-1-(2-methoxy-2-oxoethyl)-4-oxoazetidin-2-yl}-2( RS )-methyl-3-oxopentanoate which underwent fragmentation through cleavage of the N 1 –C 4 bond under the action of sodium bis(trimethylsilyl)-amide in THF at–78°C. The resulting acyclic amide, dimethyl {(2 R , S ,3 Z )-2-[(1 R )-1-{[ tert -butyl(dimethyl)-silyl]oxy}ethyl)]-4-methyl-5-oxohept-3-enoylamino}malonate, was smoothly converted to new functionalized N-substituted pyrrolidinones via intramolecular Michael type cyclization in methylene chloride in the presence of NEt 3 –DMAP–Boc 2 O.