Gold-Catalyzed Furan/Yne Cyclizations for the Regiodefined Assembly of Multisubstituted Protected 1-Naphthols

Abstract

The gold(I)-catalyzed intramolecular cycloisomerization of furan/ynes bearing a silyloxy or allyloxy group has been developed, which provides a highly efficient access to protected 1-naphthol derivatives with enal or enone moiety. The method offers several advantages such as high stereoselectivities, mild reaction conditions, and easily accessible starting materials. In addition, the naphthyl products could be further transformed into the important benzocoumarins in a one-pot procedure.

Gold‐Catalyzed Cyclization of Furan‐Ynes bearing a Propargyl Carbonate Group: Intramolecular Diels–Alder Reaction with In Situ Generated Allenes

“…When a substrate bearing an alkyl group, such as a n‐ butyl group at the propargylic position ( 12 l ), was employed, a completely different product of naphthalene 14 with a cis ‐enone moiety was obtained in 70 % yield. In this case, a competitive gold‐catalyzed cyclization of furan‐ynes with ring‐opening of the furan moiety occurred, similar to that of gold‐catalyzed cycloisomerization of TBS‐protected ( o ‐alkynyl)phenyl 2‐furylcarbinols leading to protected 1‐naphthols reported by us . This result, in which 14 was obtained, indicated that the furan‐yne cyclization occurred more rapidly than 3,3‐rearrangement of the propargyl carbonate moiety.…”

Iodine/Water‐Mediated Oxidation of o‐Alkynylaroyl Compounds and Application of the Products of Oxidation in the Synthesis of Nitrogen Heterocycles

“…However, although ketone 3f , having a nitro group on the aryl ring attached to the yne unit, afforded triketone 4f , the product could not be isolated in pure form (entry 6). The presence of heteroaryl groups was tolerated and ketones 3g and 3h afforded high yields of triketones 4g and 4h , respectively, without giving rise to any side reactions such as cycloaddition25a or electrophilic cyclisation25b (entries 7 and 8). Ketones 3i and 3j , bearing naphthyl and dibenzodioxinyl groups, respectively, also furnished the desired triketones 4i and 4j in good yields (entries 9 and 10).…”

Gold(I)‐Catalyzed Furan‐yne Cyclizations Involving 1,2‐Rearrangement: Efficient Synthesis of Functionalized 1‐Naphthols and Its Application to the Synthesis of Wailupemycin G

“…For example, in the case of gold(I)‐catalyzed cycloisomerization of furan‐ynes to protected 1‐naphthol derivatives [Scheme , Eq. (1)], the reaction proceeds via the formation of a cationic intermediate a followed by ring‐opening of the furan ring and aromatization via elimination of a proton at the benzylic position to furnish the final products 3d. We have now found that when furan‐ynes bearing a propargylic alcohol moiety such as 1 were used as the substrates, the reaction could be terminated by a 1,2‐rearrangement reaction, resulting in migration of R 2 group to vicinal carbon with simultaneous opening of the furan ring [Scheme , Eq.…”