N-heterocyclic carbene-catalyzed [4 + 2] cyclization of 2-bromo-2-enal with 3-alkylenyloxindoles: efficient assembly of spirocarbocyclic oxindole

Abstract

A NHC-catalyzed [4 + 2] cyclization of 2-bromo-2-enal bearing γ-H with 3-alkylenyloxindoles under mild reaction conditions gives spirocarbocyclic oxindoles containing one quaternary carbon in moderate to good yields with high diastereoselectivities. The easy availability of the starting materials, the concise assembly and the potential utilization value of the products make this strategy attractive in molecular biology and pharmacy.

Spiro[4H‐pyran‐3,3′‐oxindoles] Derived from 1,2,3,4‐tetrahydroquinoline—Part 2

“…compounds 2 having an oxindole nucleus but with a spirocyclic ring fused at C‐3, has been considerable, as indicated by a 2014 comprehensive review on “Recent progress on routes to spirooxindole systems derived from isatin” in this journal and a Tetrahedron Report in the same year on “Recent advances in the synthesis of biologically active spirooxindoles”. This interest continues unabated—for example we are aware of seven reports already in 2015 that deal with the conversion of isatins (1 H ‐indole‐2,3‐diones) ( 1 ) into spirooxindoles ( 2 ) (Fig. ), either directly or via a simple derivative of the isatin.…”

Spiro[3H‐pyrazole‐3,3′‐oxindoles] Derived from 1,2,3,4‐Tetrahydroquinoline

“…Interest in spirooxindoles, that is, compounds 2 having an oxindole nucleus but with a spirocyclic ring fused at C‐3, has been considerable, as one may judge from a 2014 comprehensive review on “Recent Progress on Routes to Spirooxindole Systems Derived from Isatin” in this journal and a 2014 Tetrahedron Report on “Recent Advances in the Synthesis of Biologically Active Spirooxindoles.” This interest continues unabated – for example, we are aware of six reports already in 2015 that deal with the conversion of isatins (1 H ‐indole‐2,3‐diones) into spirooxindoles .…”

Katalyse durch N‐heterocyclische Carbene über Azoliumdienolate: eine effiziente Strategie für enantioselektive Funktionalisierungen an entfernten Positionen

“…Diese Umwandlung führte in Gegenwart des achiralen NHC‐Präkatalysators C‐14 in guten Ausbeuten und mit guten bis ausgezeichneten Diastereoselektivitäten zu den spirocarbocyclischen Oxindolen 69 . Eine ähnliche Produktklasse 71 wurde durch Verwendung der α,β‐ungesättigten α‐Bromaldehyde 70 als Azoliumdienolat‐Vorstufen und des Benzimidazolsalzes C‐15 als NHC‐Präkatalysator erhalten …”