Azetidinone with enol ethers

Of the new methods of preparation of oxo derivatives of the 5,6-dihydro-4//-1,3-oxazines, the most important is that developed by Martin and co-workers 169 the reaction of acylisocyanates with enol ethers at room temperature under nitrogen yields 48 [Eq. (35)] (see also Arbuzov et a/.170-171) together with an isomeric azetidinone. The... 

Reactions of Azetidinone Sulfenic Acids with Halogenating Reagents. Conjugate Addition Reactions of Azetidinone Sulfenic Acids. Reaction of Azetidinone Sulfenic Acids with Enol Ethers. 

V. Reaction of Azetidinone Sulfenic Acids with Enol Ethers... 

As discussed in Section 2.3.3.1, enol stannyl ethers react with carbonyl compounds readily without the need for catalysts. However, catalytic amounts of AgBp4 and h have bron found to improve considerably the yield of the condensation of the tin(II) enol ether (159) with the azetidinone (93). The use of a catalytic amount of PdCl2[P(o-MeC6H4)3]2 improves the yield of the reactions between enol stannyl(IV) ethers and aldehydes. ... 

In the Kaneka approach [12], silyl enol ether 14 is obtained from the starting butyrate by sequential 0-protection, reduction to the aldehyde and treatment with TMS-Cl/TEA. Cycloaddition with CSI and reductive N-de-chlorosulfonylation with either LAH or PhSH affords azetidinone 17. Much emphasis is placed on the conversion 17 11, since 4-hydroxyazetidinones... 

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