Thio-, Amino-, and Related Claisen Rearrangement

The thermal rearrangement of allyl phenyl sulfide 48 in quinoline at 230 °C gave a 1 1 mixture of 2-methylthiacouinaran 50 and thiachroman 52 [51, 52]. 

A similar tendency was also found in the thermal reaction of propargyl phenyl sulfide. Thus, in the presence of cyclopentadiene on heating propargyl phenyl sulfide 53 in quinoline at 200 °C, thiachromen 56 and the Diels-Alder adduct 55 formed from allenyl sulfide 54 and cyclopentadiene were obtained [53]. In the absence of cyclopentadiene, a mixture of thiachromen 56 and thiacoumaren 57 was obtained. 

Heteroaromatic allyl sulfide is also a good substrate for the thio-Claisen rearrangement. One example is shown below [54]. 

The nitrogen analog of the simple Claisen rearrangement with N-allylaniUne and related derivatives is called the amino-Claisen rearrangement (or aza-Claisen rearrangement) [55]. Under thermal conditions, more drastic conditions (310-340 °C) compared with that for the oxygen substrates is required to obtain the ortho allyl aniline 59 [56]. N-Allyl aniline derivatives are, however, not stable at such 

The reaction is accelerated in the presence of a Br0nsted acid or Lewis acid. For example, in the presence of 2 N sulfuric acid, the reaction of N-crotylaniUne 60 proceeds at 60 °C to give the ortho-rearrangement product 61 in 70% yield along with a trace amount of aniline [56]. 

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