Ruthenium vinyl carbene intermediates in enyne metathesis

Diver, Steven T.

doi:10.1016/j.ccr.2006.09.008

Cited by 92 publications

(42 citation statements)

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“…[13,23] Oxidative coupling to give a metallacyclobutene, [24] with a subsequent ring opening of this species would lead to the Ru vinyl carbene II. [25] The electrophilic Ru carbene could induce a 1,5-hydride shift that would lead to the formation of a transient oxonium ion, which would in turn interact with the nucleophilic ruthenium to afford the metallacycle III. A final reductive elimination would give rise to the spiro compound 2 with recovery of the catalytic Ru II species in the presence of Table 3: Ru-catalyzed 1,5-hydride shift/cyclization sequence in alkynyl C3-linked heterocycles 10 and 11.…”

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Cyclization by Catalytic Ruthenium Carbene Insertion into CH Bonds

et al. 2011

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Novel reactions that can selectively functionalize carbon À hydrogen bonds are very important because they offer new strategic approaches in synthesis.[1] A remarkable method for such CÀH functionalization involves the insertion of metal carbenes into CÀH bonds.[2] The regioselectivity of these CÀH insertions is governed by electronic, steric, and conformational factors.[3] Typically, in nonconstrained systems, metalcatalyzed intramolecular C À H insertion reactions predominantly afford five-membered rings (1,5-insertions). [2,4] The formation of smaller and larger rings is achieved only when geometrical constraints or activated CÀH bonds are involved.[5] Usually, Rh- [6] and Cu-catalyzed [7] CÀH insertions have shown amazing versatility in both intramolecular and intermolecular reactions, but it is still a challenging goal to discover other metals and tethers that facilitate the construction of rings by C sp 3 ÀH functionalization. Recently, special attention has been paid to Pt- [8] and Au-catalyzed [9] intramolecular coupling between terminal unactivated alkynes and C sp 3 À H bonds in alkynyl ethers and amines to produce complex spiro or fused bicyclic systems by a tandem 1,5-hydride shift/cyclization sequence.[10] The above methods require temperatures as high as 100-120 8C to achieve good results and under Pt catalysis only 5-exo methylene bicyclic structures are formed. We report herein a mild procedure based on a novel tandem Ru-catalyzed carbene addition to terminal alkynes/insertion into C sp 3 À H bonds in alkynyl acetals, ethers, and amines to form complex spiro and fused bicyclic structures by 1,5-and 1,6-hydride shift/cyclization sequences (Scheme 1).[11]The cyclization of dioxolane 1 a was the first reaction examined under a variety of catalytic conditions (Table 1). After some preliminary experiments, [12] the well-known conditions, established by Dixneuf and co-workers, for the preparation of Ru carbenes starting from alkynes were employed.[13] Thus, a 1,5-hydride shift/cyclization sequence gave the functionalized spiro [5,5] compound 2 a in a moderate yield of 40 % and the linear hydroxyester 3 a as the major isolated product in 50 % yield, by stirring a dioxane solution of 1 a (0.15 m) with 1 equivalent of N 2 CHTMS (2 m in hexanes) and 10 mol % of [Cp*Ru(cod)Cl] as catalyst at 60 8C (Table 1, entry 1). A lower overall yield and a similar ratio of 2 a and 3 a were obtained when the reaction was performed in dioxane at room temperature (Table 1, entry 2). Gratifyingly, the desired spiro compound 2 a or its desilylated analogue 2 a' [13e,g] were isolated in fairly good yields (66-80 %) when the reactions were carried out in either diethyl ether or MeOH at room temperature (Table 1, entries 3 and 4). [14] However, other typical solvents like THF and toluene gave either lower yields and/or longer reaction times (Table 1, entries 5 and 6).

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Cyclization by Catalytic Ruthenium Carbene Insertion into CH Bonds

et al. 2011

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“…Initially, derivatives of the previous benchmark catalyst 10 were prepared, in which only the substituents in the ortho position of the N-aryl rings were varied (9)(10)(11)(12)(13). It is worthy to note that the syntheses of 9 and 10 are low yielding (ca.…”

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Cyclic Alkyl Amino Carbene (CAAC) Ruthenium Complexes as Remarkably Active Catalysts for Ethenolysis

et al. 2014

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An expanded family of ruthenium metathesis catalysts bearing cyclic alkyl amino carbene (CAAC) ligands is reported. These catalysts exhibited exceptional activity in the ethenolysis of the seed oil derivative methyl oleate. In many cases, TONs >100,000 were achieved, at only 3 ppm catalyst loading. Remarkably, the most active catalyst system was able to achieve a TON of 340,000, at only 1 ppm catalyst loading. This is the first time a series of metathesis catalysts has exhibited such high performance in cross metathesis reactions employing ethylene gas, with activities sufficient to render ethenolysis applicable towards the industrial scale production of linear alpha-olefins (LAOs) and other terminal olefin products.

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“…[8], and torsion angle [8]: Ru1-P1 2.4339(5), Ru1-P2 2.4478(6), Ru1-C19 1.928(2), Ru1-pCy(cg) 1.7473 (7), P1-C1 1.879(2), P1-P2 2.1771(8), P2-C19 1.759(2), C19-C20 1.480(3); P2-P1-Ru1 63.84(2), P1-P2-C19 88.26 (7), Ru1-C19-P2 83.06 (8); P1-P2-Ru1-C19 111.06 (9). (14), Ru1-C19 2.2055(14), Ru1-pCy(cg) 1.7473 (7), P1-C1 1.7926(15), P1-C19 1.7802(15), P2-C6 1.8777(15), P2-C19 1.7787 (16), C1-C2 1.486(2), C1-C6 1.547(2), C2-C3 1.351(2), C3-C4 1.461(2), C4-C5 1.341(2), C5-C6 1.518(2); C1-P1-C19-P2 2.11 (9). For an initial assessment of the reactivity of the novel h 3 -diphosphavinylcarbenes 5, we treated the ruthenacycle Ru-5 a with one equivalent tBuC P and observed the fast and selective formation of bicyclic Ru-6 b (t1 = 2 = 18 min at 0 8C; 93 % yield according to 31 P NMR spectroscopy) together with elimination of Mes*CP (Scheme 2).…”

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confidence: 98%

“…For example, reaction of alkynes with the second-generation Grubbs catalyst gives stable h 3 -vinylcarbene complexes (1, Mes = 2,4,6-Me 3 C 6 H 2 ) that form after rearrangement of the initial ruthenium cyclobutenes (B). [6,7] These puckered metal h 3 -vinylcarbene complexes [8] (C) are highly potent and represent the key intermediate in enyne metathesis, [9] alkyne polymerization (via D), [10] and the versatile Fischer carbene mediated Dötz (benzannulation) reaction (which involves complexes such as 2). [11, 12] In our quest for novel reactivity patterns and in light of the diagonal relationship between carbon and phosphorus, [13] we herein report on a diphosphorus analogue of h 3 -vinylcarbene complex C (P 2 -C).…”

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confidence: 99%

“…Finally, the subsequent electrophilic attack of P2 affords the unique Wheland product 6' (Ru: DE = À0.6, DE°= 17.7 kcal mol À1 ), of which the experimental analogues, Ru-6 b and Ir-6 b, can be isolated. [8], and torsion angle [8]: Ru1-P1 2.4339 (5), Ru1-P2 2.4478 (6), Ru1-C19 1.928 (2), Ru1-pCy(cg) 1.7473 (7), P1-C1 1.879 (2), P1-P2 2.1771 (8), P2-C19 1.759 (2), C19-C20 1.480(3); P2-P1-Ru1 63.84 (2), P1-P2-C19 88.26 (7), Ru1-C19-P2 83.06 (8); P1-P2-Ru1-C19 111.06 (9). [8]: Ru1-P1 2.3664(4), Ru1-P2 2.3863(4), Ru1-C1 2.2624 (14), Ru1-C19 2.2055(14), Ru1-pCy(cg) 1.7473 (7), P1-C1 1.7926(15), P1-C19 1.7802(15), P2-C6 1.8777(15), P2-C19 1.7787 (16), C1-C2 1.486(2), C1-C6 1.547(2), C2-C3 1.351(2), C3-C4 1.461(2), C4-C5 1.341(2), C5-C6 1.518 (2); C1-P1-C19-P2 2.11 (9).…”

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confidence: 99%

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