Cope rearrangements Brook rearrangement

Similarly, the [3 + 4] annulation of the E- and Z-isomers of /1-heteroatom-substituted acryloylsilanes 156 with lithium enolates of ,/l-unsaturated methyl ketones 157 gave stereospecifically cis-5,6- and //r/w.v-5,6-disubstituted-3-cycloheptenones 160, respectively (equation 97). The stereospecificity in the annulation was explained by an anionic oxy-Cope rearrangement of the 1,2-divinylcyclopropanediol intermediate 159, which was generated through the Brook rearrangement of the initial 1,2-adduct 158219 - 223. 

ETHENYL-4-METHOXYCYCLOBUTENE-l,2-DIONE. This procedure also provides a convenient method for the preparation of DIMETHYL SQUARATE, an important intermediate. The synthesis of (lR, 6S, 7S )-4-(tert-BUTYLDIMETHYLSILOXY)-6-(TRIMETHYLSILYL)BICYCLO-[5.4.0JUNDEC-4-EN-2-ONE is representative of a general protocol for the construction of cycloheptenones by a [3 + 4] annulation. The method features the addition of a lithium enolate to an acryloyl silane to give a 1,2-adduct that undergoes a novel sequence of a concerted Brook rearrange-ment/cyclopropanation and an anionic oxy-Cope rearrangement. 

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