Tebbe Reaction Ti

The presumed mechanism of action of the Tebbe reagent is very simple after dissociation of Me2AlCl, [2 + 2] cycloaddition of Cp2Ti=CH2 and R2C=0 is followed by [2 + 2] retro-cycloaddition to give the product. Unlike the conventional Wittig reaction, the Tebbe reaction works well with esters. 

Problem 6.26. Draw a reasonable mechanism for the following Petasis reaction. 

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