Diisobutylaluminum Hydride Promoted Cyclization of o-(Trimethylsilylethynyl)styrenes to Indenes

Abstract

The reaction of o-(trimethylsilylethynyl)styrenes with diisobutylaluminum hydride (DIBAL-H) provides 2-trimethylsilyl-1H-indenes efficiently. The cyclization mechanism involves regioselective hydroalumination of the alkynyl moiety, geometrical isomerization of the alkenylaluminums formed, and intramolecular carboalumination. With substrates bearing a 2-(trimethylsilyl)ethenyl group (R(1) = Me3Si, R(2) = R(3) = H), bis-silylated benzofulvenes are obtained upon treatment of the reaction mixture with an excess amount of benzaldehyde.

Negishi Cross-Coupling Is Compatible with a Reactive B–Cl Bond: Development of a Versatile Late-Stage Functionalization of 1,2-Azaborines and Its Application to the Synthesis of New BN Isosteres of Naphthalene and Indenyl

“…The bond distances in the six-membered azaborine ring are consistent with previously reported bond lengths for monocyclic azaborines with the exception of the bridging B–C bond (bond distance highlighted in red), which is significantly longer than that found in typical monocyclic azaborine structures (1.568(3) Å vs ∼1.52 Å) . An elongation of the bridging C–C bond in the indene/indenyl system is also observed upon deprotonation, but to a somewhat lesser extent (∼1.437 Å for Li indenyl vs ∼1.40–1.41 Å for indene). The bridging B–C distance of 1.568 Å approaches that of a B­(sp 2 )–C­(sp 2 ) single bond (e.g., 1.574 Å observed for a B -Ph-substituted 1,2-azaborine).…”

An attempt to consider cooperativity in helical-sense preferences induced in fused macrocycles

“…Tris(macrocycle)s 3 are 1,3,5-/2,4,6-differentiated hexakis(phenylethynyl)benzenes (HPEBs) 10 and we started with 1,3,5-trichloro-2,4,6-tris(2-trimethylsilylethynyl)benzene 6 . 11 Stepwise Sonogashira coupling reactions of aryl iodides ( 10 12 and 11 5 ) with desilylated acetylenes on 6 and on the resulting 7 gave trichloro-intermediates 8 . The third Sonogashira coupling of aryl acetylenes ( 12 5 ) with the chlorides 13 on 8 furnished HPEB 9 , a threefold ring-closing precursor.…”

Uncatalyzed Carbometallation Involving Group 13 Elements: Carboboration and Carboalumination of Alkenes and Alkynes

“…Mechanistic experiments showed that the intramolecular carboalumination reaction proceeded through a syn -addition. 82 83 At higher temperature, the related enyne 128 underwent skeletal rearrangement to form 1,2-dihydronaphthalen-1-ylaluminum reagent 131 via a cyclopropylcarbinylaluminum species 130 (Scheme 31b ). 84 Subsequent dehydroalumination formed the naphthalene 132 .…”