RAPID ENTRY INTO MONOCYCLIC, BICYCLIC, AND TRICYCLIC BETA-LACTAM ARRAYS VIA ALKENE METATHESIS

4-Acetoxy-2-azetidinone and -(tert-butyldimethylsilyl)-oxyethyl]-2-aze tidinone were converted into 4-alkenyloxy-, 4-(N-allyltoluene-4-sulfon amido)-, 4-(allylthio)-, and 4-alkenyl-2-azetidinone systems. In addit ion, 4-acetoxy-2-azetidinone and -(tert-butyldimethylsilyl)-oxyethyl]- 2-azetidinone were converted into beta-lactam dienes via sequential C- 4 substitution using unsaturated alcohols, allyl mercaptan, N-allyltol uene-4-sulfonamide, and allyl(chloro)dimethylsilane followed by N-ally lation. Crossed metathesis of beta-lactam alkenes with styrene partner s and ring closing metathesis of beta-lactam dienes using the Schrock (CF3)(2)MeCO](2)Mo(=CHCMe2Ph)(=NC6H3-2,6-iso-Pr-2) (1) or Grubbs Cl-2( Cy3P)(2)Ru=CHPh (2) carbenes gave diverse monocyclic and bicyclic beta -lactam systems including derivatives of 1-azabicyclo[4.2.0]octan-8-on e, 1-azabicyclo[5.2.0]nonan-9-one and its 6-thia, 6-aza, and 6-oxa ana logues, 7-oxa-1-azabicyclo[6.2.0]octan-10-one, 8-oxa-1-azabicyclo[7.2. 0]octan-11-one, and 9-oxa-1-azabicyclo[8.2.0]octan-12-one. Ring-closin g enyne metathesis and tandem ring-closing enyne and diene metathetic reactions were used to produce bicyclic beta-lactam conjugated dienes as exemplified by the conversion of -oct-7-en-2-yn-1-yl)-4-(2-propenyl )-azetidin-2-one (83) into ydro)-3-furanyl]-1-azabicyclo[4.2.0]oct-3-e n-8-one (98).