Metalation 2-azetidinones

The diazo function in compound 4 can be regarded as a latent carbene. Transition metal catalyzed decomposition of a diazo keto ester, such as 4, could conceivably lead to the formation of an electron-deficient carbene (see intermediate 3) which could then insert into the proximal N-H bond. If successful, this attractive transition metal induced ring closure would accomplish the formation of the targeted carbapenem bicyclic nucleus. Support for this idea came from a model study12 in which the Merck group found that rhodi-um(n) acetate is particularly well suited as a catalyst for the carbe-noid-mediated cyclization of a diazo azetidinone closely related to 4. Indeed, when a solution of intermediate 4 in either benzene or toluene is heated to 80 °C in the presence of a catalytic amount of rhodium(n) acetate (substrate catalyst, ca. 1000 1), the processes... 

Arylation, olefins, 187, 190 Arylketimines, iridium hydrogenation, 83 Arylpropanoic acid, Grignard coupling, 190 Aspartame, 8, 27 Asymmetric catalysis characteristics, 11 chiral metal complexes, 122 covalently bound intermediates, 323 electrochemistry, 342 hydrogen-bonded associates, 328 industrial applications, 8, 357 optically active compounds, 2 phase-transfer reactions, 333 photochemistry, 341 polymerization, 174, 332 purely organic compounds, 323 see also specific complexes Asymmetric induction, 71, 155 Attractive interaction, 196, 216 Autoinduction, 330 Axial chirality, 18 Aza-Diels-Alder reaction, 220 Azetidinone, 44, 80 Aziridination, olefins, 207... 

The method has been used most often for cyclization reactions. Five- and six-membered rings may be formed efficiently in the common cases and, when fused to an azetidinone, seven-membered rings are formed in synthetically useful yields (equation 168)327. Perhaloalkane-olefin additions have focused on intermolecular cases328 329 in some cases, yields are enhanced by the additional use of trimethylaluminum as a radical initiator328. Several other transition metal complexes are known to initiate the same processes, particularly RuCl2(PPh3)2330. 

Regio- and stereoselective metal-mediated l,3-butadien-2-ylation reactions between 1,4-dibromo-2-butyne or l,4-bis(methanesulfonyl)-2-butyne and optically pure azetidine-2,3-diones in aqueous media offers a convenient asymmetric entry to potentially bioactive 3-substituted-3-hydroxy-p-lactams 19 <02JOC1925>. In addition, 2-azetidinone-tethered 1,3-butadienes can easily be transformed into other functionalities via Diels-Alder reaction. 

Later, /J-lactams have been obtained by regiospecific metal-catalyzed ring expansion of aziridines. Treatment of A -t ri-butyl-2-phenylaziridine (252) with carbon monoxide in benzene, employing chlorodicarbonylrhodium(I) dimer as the catalyst at 90°C and 20 atm, produced the azetidinone 253 in quantitative yield. Several other )S-lactams were also synthesized from the corresponding aziridine derivatives by the application of this method, and it was noted that this reaction was completely regiospecific. The possible reaction mechanism for the formation of fi-btciams is outlined in Scheme 47. 

Bandyopadhyay D, Cruz J, Yadav RN, Banik BK (2012) An expeditious iodine-catalyzed synthesis of 3-pyrrole-substituted 2-azetidinones. Molecules 17 11570-11584 Reddy GR, Reddy TR, Joseph SC, Reddy KS, Pal M (2012) Iodine catalyzed four-component reaction a straightforward one-pot synthesis of functionalized pyrroles under metal-free conditions. RSCAdv 2 3387 3395... 

Azetidines are compounds of interest in the field of agricultural and pharmaceutical chemistry. They are also useful as monomers and cross-linkers in polymer industry. Due to ring strain associated with it, azetidines are also useful S5mthons in organic chemistry. The common methods for S5mthesis of azetidines are cyclizations of y-amino alcohols, y-amino halides, 3-amino allenes, reactions of 1,3-dielectrophiles with amines, metal-catalyzed cyclizations in diazocarbonyls, cycloaddition reactions, and reduction of 2-azetidinones. There are several reports in literature on the S5mthesis of azetidines in aqueous media. A diastereoselective synthesis of azetidines is reported by the reaction of azazirconacyclopentane derivatives with iodine followed by treatment with aqueous potassium carbonate [26]. 

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