C−H Bond Functionalization via Hydride Transfer: Direct Coupling of Unactivated Alkynes and sp<sup>3</sup> C−H Bonds Catalyzed by Platinum Tetraiodide

Vadola, Paul A.; Sameš, Dalibor

doi:10.1021/ja906480w

Cited by 176 publications

(56 citation statements)

References 30 publications

(26 reference statements)

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“…[8,9] To our delight, fused bicyclic tetrahydrofuran 12 a and piperidine 13 a were obtained in fairly good yields (Table 3, entries 1 and 2), thus showing the efficient functionalization of secondary CÀH bonds a to a heteroatom (O, N). Remarkably, a single diastereoisomer of bicyclic piperidine 13 a, containing three consecutive stereocenters, was obtained.…”

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confidence: 93%

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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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“…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.…”

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confidence: 99%

Cyclization by Catalytic Ruthenium Carbene Insertion into CH Bonds

et al. 2011

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“…7a Furthermore, Fürstner observed a 1,2-halogen shift in the phenanthrene synthesis, proceeding through the Au-vinylidene (eq 3), 8c intermediacy of which was later validated by the DFT calculations. 8d Nonetheless, evidence was accumulated in support of alternative pathways in Au-, 8e,9 Pt-, 2d,10 and even “classical” W- 11 and Ru-catalyzed 12 processes that could account for the reactivities commonly attributed to the alkyne–metal-vinylidene isomerization. This prompted us to investigate the validity of the proposed Au-vinylidene species i in the Au-catalyzed cycloisomerization of 1 (eq 1).…”

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confidence: 99%

On the Validity of Au-vinylidenes in the Gold-Catalyzed 1,2-Migratory Cycloisomerization of Skipped Propargylpyridines

Xia

Dudnik

et al. 2010

Org. Lett.

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A mechanism of the Au-catalyzed cycloisomerization of propargylpyridines has been investigated. Both DFT computational and experimental results strongly support generation of a Au-carbene via a cyclization/proton transfer sequence over the previously proposed path involving a Au-vinylidene intermediate. For the β-Si-substituted Au-carbene (G = SiR3), a 1,2-Si migration was shown to be kinetically favored over a 1,2-H shift. This study highlights importance of alternative pathways that could explain reactivities commonly attributed to an alkyne-vinylidene isomerization in Au-catalysis.

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“…Transition-metal catalysts such as complexes of gold [132,133] and platinum, [134] as well as those of cobalt [135] and palladium, [136] are used efficiently in cyclization reactions involving the intramolecular [1,5] transfer of a hydride onto a terminal alkyne or an electron-deficient alkene, followed by ring closure on the resulting stabilized carbocation (iminium-type) intermediate (Scheme 61). [132][133][134][135][136] The most typical examples of this internal redox process involve the coupling of C(sp 3 )-H bonds with double bonds (Scheme 61). [133,135,[137][138][139][140][141][142][143][144] In this process, activation of an electron-deficient alkene by a Lewis acid or transition metal initiates a 1,5-hydride transfer and the formation of a stabilized cation, which induces cyclization to form a C-C bond.…”

Section: A-c(sp 3 )-H Bond Functionalization Of Amines Via Transitionmentioning

confidence: 99%

Transition-Metal-Catalyzed Functionalization of C(sp3)&singleBond;H Bonds of Amines

Fuerstner¹,

Hall²,

Marek³

et al. 2013

Knowledge Updates 2012/4

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C−H Bond Functionalization via Hydride Transfer: Direct Coupling of Unactivated Alkynes and sp³ C−H Bonds Catalyzed by Platinum Tetraiodide

Cited by 176 publications

References 30 publications

Cyclization by Catalytic Ruthenium Carbene Insertion into CH Bonds

Cyclization by Catalytic Ruthenium Carbene Insertion into CH Bonds

On the Validity of Au-vinylidenes in the Gold-Catalyzed 1,2-Migratory Cycloisomerization of Skipped Propargylpyridines

Transition-Metal-Catalyzed Functionalization of C(sp3)&singleBond;H Bonds of Amines

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C−H Bond Functionalization via Hydride Transfer: Direct Coupling of Unactivated Alkynes and sp3 C−H Bonds Catalyzed by Platinum Tetraiodide

Cited by 176 publications

References 30 publications

Cyclization by Catalytic Ruthenium Carbene Insertion into CH Bonds

Cyclization by Catalytic Ruthenium Carbene Insertion into CH Bonds

On the Validity of Au-vinylidenes in the Gold-Catalyzed 1,2-Migratory Cycloisomerization of Skipped Propargylpyridines

Transition-Metal-Catalyzed Functionalization of C(sp3)&singleBond;H Bonds of Amines

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C−H Bond Functionalization via Hydride Transfer: Direct Coupling of Unactivated Alkynes and sp³ C−H Bonds Catalyzed by Platinum Tetraiodide