Diynes Friedel-Crafts acylation

The method is limited because of the requirement for stoichiometric reagents, but impressive applications in the preparation of complex molecules have appeared. For example, a model system for ene-diyne antibiotics has been prepared by an intramolecular route (Scheme 19). Added versatility arises from the electophilic coupling of vinyl-propargyl complexes, such as in Friedel-Crafts acylation conditions. 

Only rarely is proton loss observed from the intermediate cation derived from acylation of a terminal alkyne. In contrast, acylation of alkynylsilanes provides an excellent strategy for the synthesis of alkynyl ketones. " Here, it is apparent that elimination of the silyl substituent competes very effectively with capture of a nucleophile. Acylation of bis(trimethylsilyl)ethyne" provides a convenient route to terminal alkynic ketones, particularly since desilylation can be carried out using bases as weak as dilute aqueous borax, conditions mild enough to prevent the ready hydration of the triple bond (Scheme 25)." Silylated diynes are also excellent substrates for Friedel-Crafts acylation. ... 

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See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ ]

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