Acrylate titanium tetrachloride reaction

Hansen and colleagues177 used (+)-pantolactone as a chiral auxiliary to achieve asymmetric induction in the first step toward their synthesis of d.v-perhydroisoq uinol inc 278. The titanium tetrachloride catalyzed reaction between 1,3-cyclohexadiene (275) and chiral acrylate 276 proceeded with high diastereofacial selectivity to give 277 (94% de) in 75% yield (equation 77). 

The Diels-Alder reaction of enantiomerically pure chiral acrylic esters with cyclopentadiene leads to a pair of diastereomers. Their ratio depends strongly on the choice and amount of Lewis acid catalyst (Scheme 8). While titanium tetrachloride leads preferentially to the (2/ )-diaslcrcomer with high selectivity, ethyl aluminium dichloride gives the (2S)-diastereomer in only 56% de. 

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