No abstract

Strategic use of oxophilic (hard) gold(III) and π-philic (soft) gold(I) catalysts provides access to two types of cyclic ethers from propargylic alcohols. Thus, heating propargylic alcohols with an oxophilic gold(III) catalyst (AuBr3) results in cyclization to afford cyclic ethers bearing an acetylenic moiety, due to coordination of gold(III) to the oxygen of the propargylic hydroxyl group. On the other hand, propargylic alcohols with a π-philic gold(I) catalyst (Ph3PAuNTf2) induces Meyer-Schuster rearrangement to afford α,β-unsaturated ketones, which undergo gold(III)-catalyzed intramolecular oxa-Michael addition to afford cyclic ethers bearing a carbonyl group, due to coordination of gold(III) to the oxygen of the carbonyl group.

Der Titelligand wird in seiner rac. Form (IIa) ausgehend vom Diol (I) über sein Dibromid, dessen Behandlung mit tert.‐Butyl‐Li und nachfolgender Umsetzung mit Chlorodiphenylphosphin dargestellt.

Gold(I)/(III)-Catalyzed Synthesis of Cyclic Ethers; Valency-Controlled Cyclization Modes. -Two types of cyclic ethers are obtained from propargylic alcohols by gold(I)/(III)-catalyzed regiodivergent syntheses. Use of an oxophilic gold(III) catalyst provides access to cyclic ethers bearing an acetylenic moiety. On the other hand, treatment of propargylic alcohols with a -philic gold(I) catalyst induces a Meyer--Schuster rearrangement leading to ,-unsaturated ketones. The latter undergo gold(III)-catalyzed intramolecular oxa-Michael addition affording cyclic ethers bearing a carbonyl group. -(MORITA*, N.; YASUDA, A.; SHIBATA, M.; BAN, S.; HASHIMOTO, Y.; OKAMOTO, I.; TAMURA, O.; Org. Lett. 17 (2015) 11, 2668-2671, http://dx.doi.org/10.1021/acs.orglett.5b01046 ; Showa Pharm. Univ., Machida, Tokyo 194, Japan; Eng.) -Toeppel 41-043