Science of Synthesis

López-Carrillo, V.; Echavarren, A. M., Science of Synthesis Knowledge Updates, (2011) 2, 101.

Gold(I) salts and complexes are the most alkynophilic amongst the electrophilic metals that catalyze cyclization of 1,n-enynes.[‌1‌–‌13‌] Gold(I) complexes are highly selective Lewis acids with a high affinity for π-bonds linked to relativistic effects, which reach a maximum with gold.[‌6‌,‌14‌–‌16‌] In the reactions of 1,6-enynes ‌1‌, the alkyne group is selectively activated by a cationic gold species {[AuL]+} to form an alkyne–gold(I) complex, which reacts intramolecularly with the alkene by formal 5-exo-dig or 6-endo-dig cyclization to form intermediates ‌2‌ and ‌3‌, respectively (‌Scheme 1‌).[‌1‌] A number of alkyne–gold complexes have been characterized[‌17‌–‌21‌] and studied in solution.[‌22‌–‌25‌]

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References