Bi(OTf)₃-Mediated Intramolecular Olefinic Cyclization: Synthesis of Substituted Aryl-Dihydronaphthalenes and Indenes

Abstract

In this article, a facile two-step and one-pot synthetic route for the preparation of substituted aryl dihydronaphthalenes starting from 2-allylbenzaldehydes via Grignard 1,2-addition and Bi(OTf)-catalyzed intramolecular olefinic cyclization has been developed. A five-membered ring indene skeleton is also prepared via olefin isomerization, 1,2-addition followed by cyclization. Some key structures are determined using single-crystal X-ray crystallography. A possible mechanism is presented herein.

Bismuth(III) triflate: An Efficient Catalyst for the Synthesis of Diverse Biologically Relevant Heterocycles

“…In this context, last decade has seen a tremendous outburst of the applications of various metal‐triflates as Lewis acidic catalysts for the diverse organic synthesis . In recent time bismuth (III) salts as catalyst have gained significant attention for organic transformations . In 1997, Dubac and his group first employed bismuth(III) trifluoromethanesulfonate [Bi(OTf) 3 ] as a catalyst .…”

<strong>A one-pot microwaves-mediated approach towards 3-methylisoquinolines from hydrazone-derived 1-azatrienes</strong>

“…The isomerization of 2-allylbenzaldehyde (4) by RuClH(CO)(PPh3)3 catalysis allowed the obtention of the ortho-propenylbenzaldehyde 5 in good yield and acceptable E:Z selectivity (90%, E:Z = 82:18, Scheme 2). However, treatment with sodium hydroxide in refluxing methanol, as reported by Chang et al, [7] resulted in the isomerization of 4 with acceptable yield and good E:Z selectivity (80%, E:Z = 95:5 to 100:0).…”

“…The strategy involved a first step of obtaining hydrazone-derived 1-azatrienes ( 6), followed by the change of solvent and a microwave-assisted electrocyclization reaction, all in the same reaction pot. It was found that the reaction invariably led to the formation of 3-methylisoquinoline (7,IQ) with yields between 5% and 73%, together with 3,4-dihydroisoquinoline (8, DHIQ) as a secondary product, with yields between 9% and 38%. The best results (yield and IQ:DHIQ ratio) were found when N,N-dimethylhydrazine (Y = NMe2; yield = 85%; IQ:DHIQ = 1:0.16) and semicarbazide [Y = NHC(O)NH2; yield = 93%; IQ:DHIQ = 1:0.7] were employed.…”

Recent Advances in the Synthesis of Indenes

“…In 2017 Chan reported an efficient Bi(OTf) 3 ‐catalyzed intramolecular cyclization of aryl‐substituted benzylic alcohol for the preparation of substituted aryl‐dihydronaphthalenes and indenes. While the 1,2 addition of the 2‐allylbenzaldehyde 169 with a Grignard reagent followed by Bi(OTf) 3 ‐catalyzed intramolecular olefinic cyclization provided aryl‐dihydronaphthalenes 170 , the same reaction performed on vinylbenzaldehyde 171 allowed to achieve substituted aryl‐indenes 172 in excellent yields (Scheme ).…”