Ortho-hydroxychalcones

A similar study has been reported with ortho-hydroxychalcones in dry media on silica gel [107]. Conventional thermal cydization, under the same conditions as for microwave irradiation, required a much longer reaction period (Eq. (57), Tab. 3.24, and Scheme 3.18). 

Phenol esters of a,(3-unsaturated carboxylic acids have an interesting reactivity due to the synthetic utility of the resulting hydroxychalcones (Scheme 19). This aspect will be illustrated in Section IV. However, from the basic point of view, it is worth mentioning that the cis or trans configuration of the olefinic part of the acyl moiety can have a marked influence on the photochemical reactivity of the ester. When para-methoxyphenyl fumarates are irradiated, the normal ortho-rearranged products are obtained. By contrast, irradiation of para-me-thoxyphenyl maleates does not lead to rearrangement. Instead, cyclization products are obtained (Scheme 20). 

Unusual Friedel-Crafts reactions, IX. One-step ortho-acylation of phenols with a,(3-unsaturated acyl chlorides. Synthesis of 2 -hydroxychalcones and sorbicillin analogues. Tetrahedron 40 4081-4084. 

---

See also in sourсe #XX -- [ ]

---