1,3-Dioxycyclopentadienes from (1-Alkynyl)carbene Tungsten Complexes - Domino Cyclization/Cycloaddition Reactions

Abstract

1,3-Dioxytetrahydropentalenes 9 have been generated by base-catalyzed addition of protic oxygen nucleophiles ROH 6a-g (RO = carboxy or phenyloxy) to the [2-(1-cyclopentenyl)ethynyl]carbene tungsten complex 3. Compounds 9 are highly reactive and afford (cyclobutenyl)carbene complexes 12a-g through spontaneous [2+2] cycloaddition to a second

Bicyclic Cyclopentadienes with N,S Substituents

“…8 13 C NMR (C 6 D 6 ): δ ϭ 161.1 (C q , C2 Py), 149.6, 135.9, 122.8, and 120.0 (CH each, Py), 151.2 (C q , C10), 146.2 (C q , C18), 142.1 (CH, C19), 137.7 (C q , C2), 126.9 (C q , C3), 119.5 (C q, C11), 93.5 (C q , C12), 69.5 (CH, C13), 68.3 (10-OCH 2 ), 61.5 (12-OCH 2 ), 61.0 (C q , C10), 67.6 (CH, C9), 56.7 (C q , C1), 31. 5 (3aR*)-3-Ethoxy-4,5,6,7-tetrahydro-3aH-inden-1-yl (1E)-N-Phenylethanimidothioate (12b) and Pentacarbonyl(N-phenylthioacetamide-S)tungsten (13): Pentacarbonyl(3-cyclohexenyl-1-ethoxy-2-propyne-1-ylidene)tungsten (1b) (243 mg, 0.50 mmol) was treated with 2 equiv.…”

“…by addition of enamines [4] or by addition of a variety of different protic nucleophiles NuH [e.g. RCϭNR(RЈCO)CH 2 , [5] R 2 NH, [6,7] R 2 PH, [8] RC(ϭO)OH and ROH, [8,9] RC(ϭX)SH (X ϭ O, NH, NR) [10] and RSH [11] ]. [6,12] The latter procedure was shown to be well suited for the generation of highly reactive bicyclic cyclopentadienes, such as tetrahydropentalenes [5,6] or tetrahydroindenes, [7,8] and most notable also for the attachment of anionic substituents to the cyclopentadiene ring, which is not achieved by more conventional routes.…”

“Dimers” and “Trimers” of Tetrahydroindenes and Hexahydroazulenes, Respectively Generated from [2-(1-Cycloalkenyl)ethynyl]carbene Complexes (M=W, Cr) by Cascade Cyclization/Cycloaddition Reactions

“…[6,13,14] Most notably, the 13 C NMR shift of the WC unit, d 319.2, is observed in a range characteristic of nonconjugated 1-tungsta-1,3,5-hexatrienes, thus indicating a presumably strong distortion of the WC unit relative to the CC unit and only slight p conjugation resulting from it. Structural characteristics of compound 16 were determined by a crystal structure analysis ( Figure 2).…”

“…[2] We previously reported on the formation of cyclopentadiene rings [3] by p cyclization of 1-metalla-1,3,5-hexatrienes, [4] which were generated from [2-(1-cycloalkenyl)ethynyl]carbene complexes 1 a ± d by addition of protic nucleophiles NuH (NuH R 2 NH, [5] R 2 PH, [5] RC(O)OH and ROH, [6] RC(X)SH (X O, NH, NR), [7] and RSH [1] ). [8] Whilst addition of nitrogen, phosphorus, and sulfur nucleophiles resulted in production of cyclopentadiene complexes, oxygen nucleophiles afforded metal-free cyclopentadienes.…”

“…It was shown, for example, that addition of ROH (R aryl, aroyl, and acyl) to the [2-(1-cyclopentenyl)ethynyl]carbene tungsten complex 1 a gave highly reactive tetrahydropentalenes 4 through p cyclization of the 1-tungsta-1,3,5hexatriene intermediates 3 (Scheme 1). [6] Compounds 4 underwent a cascade of reactions, initiated by [22] cycloaddition with (1-alkynyl)carbene complex 1 a to give compounds 5, from which pentacyclic compounds 6 were finally derived. The reaction between the tetrahydropentalenes 4 and (1-alkynyl)carbene complex 1 a was regioselective and highly exo stereoselective.…”