Isoflavones, synthesis from chalcones

Three highly useful synthetic transformations are presented in this section the synthesis of isoflavones from chalcones, the synthesis of a-arylalkanones fmm arylalkenes, and the synthesis of a-arylalkanoic acids from aryl ketones. Two others are potentially useful methods, but are not as yet widely used the preparation of a-branched carboxylic acids from a ynes, and the ring expansion and ring contraction of cyclic alkenes and ketones. 

The treatment of various chalcones 210 with HTIB or DAIB-TSOH in a methanolic medium leads to the / -keto dimethylacetals 211 (Scheme 59) (02S2490). This rearrangement can also be effected with poly[4-(diacetoxy)-iodo]styrene and has been developed into a one-pot synthesis of isoflavones (e.g., 213) from benzoyl-protected 2/-hydroxychalcones (e.g., 212), via base-catalyzed cyclization of the acetal intermediates. 

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