Ring closure strategy

Xie and co-workers developed a simple route for the synthesis of 3-aryl-l,2,3,4-tetrahydroquinolines 79 using a direct intramolecular reductive ring closure strategy <06TL7191>. The yields for the key reductive ring closure were moderate however, the simplicity of their route leads to an efficient synthesis of a variety of tetrahydroquinolines 79. 

Scheme 4 Different Ring Closure Strategy for Oxazolidinone In The Synthesis of Linezolid and Rivaioaban...

Scheme 1 Radical-mediated ring closure strategies...

Ring-closed analogue of nicotine. The following example illustrates a very intriguing result with natural (S)-(—)-nicotine. The ring-closure strategy yielded a compound which possesses the same pharmacological profile as nicotine but which totally fails to compete for [ H]-nicotine... 

A final mention of Kamiya disulfides in penem synthesis relates to their use as intermediates for 4-chloroazetidinones these in turn can be converted to 4-thioesters [55]. However, chlorinolysis of azetidinone-4-sulfides and -disulfides finds its most important application in the 1,5-ring closure strategy to penems, so that it will be discussed at a later point in this review. 

It is tempting to analyze the relative ease of the ring closure strategies to biocyclic J-lactam antibiotics in the light of Baldwin s rules [205a]. The intramolecular additions referred to above are disfavored, although the rules are less... 

Michael-type Additions and MIRC (Michael Initiated Ring Closure) Strategy... 

Molina P, Arques A, Vinader M. V. Fused pyrimidines by a tandem aza-Wittig/elec-trocyclic ring closure strategy synthesis of p5rrazolo[3,4-d]pyrimidine, [l,2,3]triazo-... 

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