Pt^II‐Catalyzed Synthesis of 9‐Oxabicyclo[3.3.1]nona‐2,6‐dienes from 2‐Alkynyl‐1‐carbonylbenzenes and Allylsilanes by an Allylation/Annulation Cascade

Abstract

Platin ist der Schlüssel: PtII‐Ionen katalysieren die Synthese von 9‐Oxabicyclo[3.3.1]nona‐2,6‐dienen aus leicht erhältlichen 2‐Alkinyl‐1‐carbonylbenzolen, Allylsilanen und Wasser (siehe Schema). Die Reaktionsfolge umfasst vermutlich drei Schritte: Allylierung der Carbonylgruppe, Hydroalkoxylierung der Alkineinheit und eine neuartige En‐Oxonium‐Anellierung.

Chiral Silver Phosphate Catalyzed Transformation of ortho‐Alkynylaryl Ketones into 1H‐Isochromene Derivatives through an Intramolecular‐Cyclization/Enantioselective‐Reduction Sequence

“…The introduction of a fluoro substituent on the tethering benzene ring of a diarylsubstituted ketone (substrate 2 o) did, however, result in a slight decrease in chemical yield, but with little detrimental effect on the enantioselectivity ( Table 3, entry 14). 1-Allyl 1H-isochromenes, such as 4 q, have been utilized as key intermediates for the synthesis of the 9-oxabicyclo[3.3.1]nona-2,6-diene framework, [18] and this bicyclic ring structure has been found in some biologically active molecules. Finally, the synthetic utility of the present method was demonstrated (Scheme 3).…”

Gold‐Catalyzed, Intramolecular, Oxygen‐Transfer Reactions of 2‐Alkynyl‐1,5‐diketones or 2‐Alkynyl‐5‐ketoesters: Scope, Expansion, and Mechanistic Investigations on a New [4+2] Cycloaddition

“…Hence, using alkynyldiketone 1 b- O under acidic conditions (Scheme 4). [26] The 18 O exchange occurred only on the methyl carbonyl group, as indicated by 13 C NMR spectroscopy. A 0.05 ppm (5 Hz) upfield chemical shift [25] was found on carbon 1 in the substrate, whereas no chemical shift change occurred on carbon 2. ]…”

“…Afterwards the solvent was removed under reduced pressure and the residue was subjected to a flash column chromatography (eluent: ethyl acetate/nhexane = 1:15) to give product 2 a (45 mg, 98 %) as a colorless oil. 1 H NMR (CDCl 3 , 500 MHz): d = 1.58 (s, 3 H), 1.70 (s, 3 H), 2.14-2.18 (m, 1 H), 2.48-2.53 (m, 1 H), 2.56-2.61 (m, 1 H), 2.76-2.78 (m, 1 H), 7.39-7.55 (m, 6 H), 7.48-7.84 ppm (t, J = 7.0 Hz, 4 H); 13 C NMR (CDCl 3 , 126 MHz): d = 17.2, 24.5, 36.0, 38.5, 65.5, 128.1, 128.4, 128.5, 129.3, 131.4, 132.4, 137.3, 139.4, 140.8, 148.7, 196.5, 204.5 ppm;IR (neat): ñ = 2968IR (neat): ñ = , 2930IR (neat): ñ = , 1673IR (neat): ñ = , 1645IR (neat): ñ = , 1596IR (neat): ñ = , 1446IR (neat): ñ = , 1283 À1 ; elemental analysis calcd (%) for C 21 H 20 O 2 : C 82.86, H 6.62; found: C 82.68, H 6.76. …”

Copper‐Catalyzed Cascade Cyclization of Indolyl Homopropargyl Amides: Stereospecific Construction of Bridged Aza‐[n.2.1] Skeletons

“…PG = protecting group. In addition, amides containing different substituents on the indole ring also underwent smooth cascade cyclization,p roducing the corresponding 2f-n in good to excellent yields (entries [6][7][8][9][10][11][12][13][14], Finally,i tw as found that the reaction also occurred well with (S)-(+ +)-tert-butylsulfinamide-derived 1e' ',a nd thus the other enatiomer, 2e' ', was specifically produced (entry 15). Further screening of solvents such as toluene and chlorobenzene led to as lightly decreased yield (entries [14][15].…”

“…[9a,b] On the basis of this work, the relevant tandem exo-hydroalkoxylation/hydroarylation was further developed by the same group. [10] In 2015, Yang and co-workers demonstrated an elegant approach for the efficient synthesis of oxabicyclo-[3.2.1]octanes by ag old-catalyzed exo-hydroalkoxylation/ semi-pinacol rearrangement (Scheme 1d). [10] In 2015, Yang and co-workers demonstrated an elegant approach for the efficient synthesis of oxabicyclo-[3.2.1]octanes by ag old-catalyzed exo-hydroalkoxylation/ semi-pinacol rearrangement (Scheme 1d).…”