Sigmatropic rearrangements

5 real reactions from the literature: [1,5]-H sigmatropic shift on cyclic conjugated dienes; Claisen rearrangement on allyl aryl ethers and acetals; other sigmatropic rearrangement on conjugated trienes. Each scheme shows starting materials, conditions and products, with the yield and reference where the source reports them.

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1. [1,5]-H sigmatropic shift: a cyclic conjugated diene with 225 C; [1,5] H shift gives the isomerized diene.

   [1,5]-H sigmatropic shiftHelv. Chim. Acta 1970, 53, 173

2. Claisen rearrangement: 1-methoxy-2-prop-2-enoxybenzene (an allyl aryl ether) with Δ gives 6-allylguaiacol (the γ,δ-unsaturated carbonyl).

   Claisen rearrangementOrg. Synth. Coll. Vol. 3, p. 418

3. Other sigmatropic rearrangement: 1,2-bis[(Z)-prop-1-enyl]benzene (a conjugated triene) with 6e dis; [1,7] H shift gives the rearranged triene.

   Other sigmatropic rearrangementHelv. Chim. Acta 1970, 53, 173

4. [1,5]-H sigmatropic shift: a cyclic conjugated diene with 240 C; [1,5] H shift gives 1,2,3-triphenyl-1H-indene (the isomerized diene).

   [1,5]-H sigmatropic shiftJ. Am. Chem. Soc. 1971, 93, 650

5. Claisen rearrangement: 1,1-bis[(prop-2-en-1-yl)oxy]cyclohexane (an acetal) with p-TsOH, Δ; toluene gives 2-prop-2-enylcyclohexan-1-one (the γ,δ-unsaturated carbonyl).

   Claisen rearrangementOrg. Synth. Coll. Vol. 5, p. 25