October   2010
Four-ring Compounds, the feature products of IS Chemical Technology. They are useful pharmaceutical intermediates used for the preparation of allergic rhinitis drugs and oral carbapenem antibiotics.

Synthesis of Four-ring Compounds.


The dialkyl malonate (2.0 mol) was added to a stirred suspension of sodium hydride (2.2 mol) in dry DMF (750 mL) below 70 oC. On cessation of hydrogen evolution, the dibromide (267 g, 1.0 mol) was added in one portion and the mixture heated for 24-48 h. The reaction mixture was cooled and poured into an aqueous solution of ammonium chloride (100 g in 1.6 L), to prevent emulsion formation, and extracted with hexane. The combined extracts were then washed with water and sodium hydrogen carbonate solution and dried over magnesium sulfate, and the solvent was evaporated. Distillation of the residue through a short Vigreux column afforded a mixture of products in the more volatile fraction.
Diisopropyl3,3-dimethoxycyclobutane-1,l-dicarboxylat (287.5 g, 1.0 mol) was stirred with 20% hydrochloric acid (750 mL) at reflux for 60 h. After cooling, the solution was continuously extracted with ether for 18 h. The ether was removed at reduced pressure, leaving yellow oil, which crystallized on standing and proved to be the title acid (111 g, 97%).


Stirring epichlorohydrin and benzhydrylamine in methanol (25 oC/7 d, 50 oC /7 d, then 25 oC /18 d) gave the azetidinol in 51% yield.

The application of Four-ring Compounds.




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