Chromate ester 3,3 -sigmatropic rearrangement

The first step in Cr(VI) oxidations can take place to give a chromate ester (Chapter 24) but this intermediate has no proton to lose so it transfers the chromate to the other end of the allylic system where there is a proton. The chromate transfer can be drawn as a [3,3]-sigmatropic rearrangement. 

This is probably a [3,3] sigmatropic rearrangement 112 of the chromate ester of the tertiary alcohol so that 109 is oxidised directly to 111 via the chromate ester 113 without any secondary alcohol 110 actually being formed. An important way to carry out this strategy appears in chapter 18 under the Heck reaction. 

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