Rearrangements reaction with Grignard reagents

A new approach to this synthesis category involves the dimerization of halogenated oxime ethers 705 by reaction with Grignard reagents, where the C-2 atom of the product 706 arises from a rearrangement that is proposed to proceed via azirene intermediates <2002JA9032, 2004CL122>. 

The reactions of the isocyanurates have been reviewed previously (59HC(13)1, p.389). The following discussion will concentrate on three facets of isocyanurate chemistry ring cleavage, reactions with Grignard reagents and rearrangements. 

For this reason, the halogen of or-haloethers or -thioethers is very reactive in S l reactions, and such compounds should also be prime candidates for an I mechanism in their reaction with Grignard reagents. As noted above (Section 2.2.2), these reactions do occur very readily and often in good yield, and a carbocation is the consensus intermediate 104]. In the reactions collected in Table 2.3. the predominance of retention in entries. 3 and 6 and the probable carbocation rearrangement product in entry 5 might be noted. 

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