Carbapenem

Alkynes undergo stoichiometric oxidative reactions with Pd(II). A useful reaction is oxidative carboiiyiation. Two types of the oxidative carbonyla-tion of alkynes are known. The first is a synthesis of the alkynic carbox-ylates 524 by oxidative carbonylation of terminal alkynes using PdCN and CuCh in the presence of a base[469], Dropwise addition of alkynes is recommended as a preparative-scale procedure of this reation in order to minimize the oxidative dimerization of alkynes as a competitive reaction[470]. Also efficient carbonylation of terminal alkynes using PdCU, CuCI and LiCi under CO-O2 (1 I) was reported[471]. The reaction has been applied to the synthesis of the carbapenem intermediate 525[472], The steroidal acetylenic ester 526 formed by this reaction undergoes the hydroarylalion of the triple bond (see Chapter 4, Section 1) with aryl iodide and formic acid to give the lactone 527(473],... 

Depending on the substituents of l,6-enynes, their cyclization leads to 1.2-dialkylidene derivatives (or a 1.3-diene system). For example, cyclization of the 1,6-enyne 50 affords the 1.3-diene system 51[33-35]. Furthermore, the 1.6-enyne 53, which has a terminal alkene, undergoes cyclization with a shift of vinylic hydrogen to generate the 1,3-diene system 54. The carbapenem skeleton 56 has been synthesized based on the cyclization of the functionalized 1,6-enyne 55[36], Similarly, the cyclization of the 1,7-enyne 57 gives a si -mem-bered ring 58 with the 1,3-diene system. 

ANHBIOHCS - BETA-LACTAMS - CARBAPENEMS AND PENEMS] pol 3) 1-Dehydropiperidine [28299-36-7]... 

---