Rearrangement Super hydride

Both Parsons [49] and Mulzer [50, 51] used related Eschenmoser-Claisen rearrangements to set a benzylic quaternary stereocenter in their approach to morphine alkaloids (Scheme 7.25) [5, 52, 53]. Reduction of cyclohexenone 65 followed by Eschenmoser-Claisen rearrangement gave unsaturated amide 66, which was subsequently converted into a known precursor of morphine (Scheme 7.24, Eq. 1). Treatment of the acid sensitive phenanthrenol 67 with dimethylacetamide dimethyl acetal (4) afforded amide 68 comprising the entire carbon skeleton of the morphine (Eq. 2). The amide was subsequently reduced to a primary alcohol (69) using lithium triethylborohydride (Super-Hydride), the most suited reagent to perform this task. Previous total syntheses of the alkaloid were intercepted at the stage of dehydrocodeinone. 

It is likely that protonated cyclopropane transition states or intermediates are also responsible for certain non-1,2 rearrangements. For example, in super acid solution, the ions 15 and 17 are in equilibrium. It is not possible for these to interconvert solely by 1,2-aIkyl or hydride shifts unless primary carboca-tions (which are highly unlikely) are intermediates. However, the reaction can be explained by postulating that (in the forward reaction) it is the 1,2 bond... 

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