PtCl₂‐Catalyzed Hydrative Cyclization of Trialkyne Functionalities to Form Bicyclic Spiro Ketones

Abstract

Triple rounds: A regioselective hydrative cyclization of triynes has been developed to give bicyclic β‐hydroxy spiro ketones, which undergo subsequent dehydration to give the β,γ‐unsaturated ketones (see scheme). Model reactions suggest that this platinum catalysis includes two selective hydrations, an alkyne insertion, and an aldol condensation.

An Extremely Simple Dibenzopentalene Synthesis from 2‐Bromo‐1‐ethynylbenzenes Using Nickel(0) Complexes: Construction of Its Derivatives with Various Functionalities

“…Trimethylsilylacetylene was purchased from Shin-Etsu Chemical Co., Ltd. Compounds 9 [15] and 16, [16] 3-bromo-4-iodotoluene, [17] 4-bromo-5-iodo-1,2-dimethoxybenzene, [18] and methyl 3-bromo-4-iodobenzoate [19] were prepared according to previously reported procedures.…”

Hypervalent‐Iodine‐Mediated Cascade Annulation of Diarylalkynes Forming Spiro Heterocycles under Metal‐Free Conditions

“…The cascade annulation of internal alkynes bearing aryl ring(s) is a useful synthetic strategy for the construction of bridged3 or spiro4 polycyclic rings. A literature survey reveals the following existing methods: 1) Pd II /I III ‐mediated intramolecular annulation of internal alkynes through successive CN‐bond formations (Scheme a),3a 2) Pd II ‐catalyzed intramolecular diamination of diarylacetylene accompanied by C(sp 3 )N bond cleavage to afford bioactive indoloisoquinolinones (Scheme b),3c 3) Pt II ‐catalyzed hydrative cyclization of trialkynes to form bicyclic spiro ketones (Scheme c),4a and 4) Pd II ‐catalyzed cascade reactions of alkyne intermediates leading to the construction of spiro[indoline‐3,3′‐quinoline] derivatives (Scheme d) 4b. However, it is evident that all of the existing methods require the use of a transition‐metal catalyst.…”

An Expeditious Synthesis of 8-Methoxy-1-tetralone

“…Based on these results, we realized that this methodology could represent an efficient approach to the synthesis of 1 provided that C4 of the aromatic ring was blocked, in order to direct the intramolecular acylation to C2, with a substituent easily removed after the cyclization step (Scheme 3). Thus, the modified synthetic route started with the bromination of methyl ester 4, obtained as previously described, with NBS under the conditions reported by Chang and co-workers 20 to provide 5 in excellent yield (98%), along with traces of the dibrominated analogue 10. Cyclization of 5 with Eaton's reagent afforded 5-bromo-8-methoxy-1-tetralone (6) in 95% yield.…”