Gold(I)‐Catalyzed Cycloisomerization of 3‐Methoxy‐1,6‐enynes Featuring Tandem Cyclization and [3,3]‐Sigmatropic Rearrangement

Bae, Hyo Jin; Baskar, Baburaj; An, Sang E.; Cheong, Jae Y.; Thangadurai, T. Daniel; Hwang, In‐Chul; Rhee, Young Ho

doi:10.1002/anie.200705117

Cited by 102 publications

(35 citation statements)

References 48 publications

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“…5 We first reasoned that the introduction of this substituent onto the oxygen would suppress the formation of 3 (path B, Scheme 2), because of the reduced bacisity of t-Boc group. Unlike our previous studies, 3,4 pathway A would prevail in this case. Moreover, this new catalytic reaction will provide synthetically useful cyclohexane-1,2-diol compounds possessing exo-olefins at the 4-position (2, in Scheme 1).…”

contrasting

confidence: 47%

“…Recently, we discovered gold(I)-catalyzed cycloisomerization of 3-methoxy-1,6-enynes, invoking heterocyclization and the subsequent [3,3]-sigmatropic rearrangement as the key mechanism. 3 Further investigation of 3-siloxy-1,6-enynes led to the development of unprecedented gold(I)-catalyzed divergence between pinacol-terminated vs. Claisen-terminated cyclization cascades.…”

mentioning

confidence: 99%

“…3 Further investigation of 3-siloxy-1,6-enynes led to the development of unprecedented gold(I)-catalyzed divergence between pinacol-terminated vs. Claisen-terminated cyclization cascades. 4 These examples indeed illustrate that the reactivity of 3-alkoxy-1,6-enynes in the divergent pathway can be controlled by the subtle variation of the substituents on the alkoxy group.…”

mentioning

confidence: 99%

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Gold(I)-catalyzed Tandem Cyclization of 3-(tert-Butoxycarbonyloxy)-1,6-enynes

Cheong¹,

Bae²,

Baskar³

et al. 2009

Bulletin of the Korean Chemical Society

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Over the past decade, there has been explosive interest in the area of new homogeneous gold-catalyzed reactions.1 The capability of cationic gold(I) species that activates alkynes towards heteroatom and carbon nucleophiles led to the discovery of numerous novel catalytic transformations. Diverse structures generated by these reactions make this process a very powerful strategy for organic synthesis. Tandem reactions of 1,n-enyne substrates are particularly interesting in this regard.2 Our interest in this area has focused on the divergent reactivity of 3-alkoxy-1,6-enynes. A salient feature of these types of substrates is that oxygen atom and the olefin can compete in the addition to the gold-bound alkynes. This competition may lead to synthetically important structural motifs via catalytic tandem reactions.Recently, we discovered gold(I)-catalyzed cycloisomerization of 3-methoxy-1,6-enynes, invoking heterocyclization and the subsequent [3,3]-sigmatropic rearrangement as the key mechanism.3 Further investigation of 3-siloxy-1,6-enynes led to the development of unprecedented gold(I)-catalyzed divergence between pinacol-terminated vs. Claisen-terminated cyclization cascades. 4 These examples indeed illustrate that the reactivity of 3-alkoxy-1,6-enynes in the divergent pathway can be controlled by the subtle variation of the substituents on the alkoxy group. In an effort to expand the scope of the catalytic reactions associated with the 3-alkoxy-1,6-enynes, we pursued further variation of the alkoxy moiety. In particular, we considered using 3-(t-butyloxycarbonyl)oxy-1,6-enynes 1 (Scheme 1), based on the recent reports on the use of t-butyloxycarbonyl (t-Boc) group in gold(I)-catalyzed domino processes. 5 We first reasoned that the introduction of this substituent onto the oxygen would suppress the formation of 3 (path B, Scheme 2), because of the reduced bacisity of t-Boc group. Unlike our previous studies, 3,4 pathway A would prevail in this case. Moreover, this new catalytic reaction will provide synthetically useful cyclohexane-1,2-diol compounds possessing exo-olefins at the 4-position (2, in Scheme 1).Our rationalization in terms of the competing pathways was justified when we examined substrate 4. Using electron poor ligand 6a (5 mol%) with AgSbF6 (5 mol%) provided the product 5 in only 32% NMR yield, although the starting material was completely consumed within 10 min (entry 1). In this preliminary study, no apparent formation of the cycloheptene product 3 generated via path B was observed. Using a more electron-donating ligand 6b (5 mol%) somewhat improved the yield of 5 (entry 2). A significant increase of the yield arises when more electron-donating ligand 6c (5 mol%) was employed (entry 3) In this case, the product was obtained in 76% isolated yield after 10 min. Delightedly, reducing the catalyst loading to 2 mol% still maintained the catalytic activity with slight decrease in the yield of the desired transformation

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confidence: 47%

mentioning

confidence: 99%

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confidence: 99%

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Gold(I)-catalyzed Tandem Cyclization of 3-(tert-Butoxycarbonyloxy)-1,6-enynes

Cheong¹,

Bae²,

Baskar³

et al. 2009

Bulletin of the Korean Chemical Society

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“…Thus, enantioenriched indenyl ethers have been produced from benzylic ethers in the transformation shown in 72 . Rhee and coworkers exploited a similar reactivity using cationic gold(I) complex Ph 3 PAuCl/AgSbF 6 on 3-methoxy-1,6-enynes 73 . In this case, due to the lack of stabilization at the benzylic position, seven-membered rings were obtained.…”

Section: Ether Migrationsmentioning

confidence: 99%

Gold‐Catalyzed Migrations and Ring Expansions

Merino

Fernández

Nevado

2014

Patai's Chemistry of Functional Groups

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Gold complexes have been used to π‐activate alkynes, alkenes, and related moieties due to their strong affinity for these carbon systems. In this chapter we have summarized first, the most representative examples of gold‐catalyzed migrations occurring in propargylic systems and classified them according to the nature of the migrating group. In the second part, we have compiled the most relevant gold‐catalyzed ring expansions according to ring size. The current mechanistic understanding of these transformations is also presented.

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“…Rhee has reported the gold(I)-catalyzed cycloisomerization of 3-methoxy-1,6-enynes to form 1-methoxy-1,4-cycloheptadienes (Eq. (12.28)) [88]. The course of the gold(I)-catalyzed cyclization of 3-silyloxy-1,6-enynes depends on the nature of the supporting ligand.…”

Section: Ethers and Epoxides As Nucleophilesmentioning

confidence: 99%

Gold‐Catalyzed Addition of Oxygen Nucleophiles to CC Multiple Bonds

Widenhoefer

Song

2010

Catalyzed Carbon‐Heteroatom Bond Formation

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The direct, catalytic addition of an oxygen nucleophile to a CÀC multiple bond represents an attractive approach to the formation of CÀO bonds from simple, readily available precursors. For this reason, there has been considerable interest in the identification of new and effective catalysts for the addition of oxygen nucleophiles to CÀC multiple bonds. One of the most significant developments in homogenous catalysis over the past 5-10 years has been the emergence of soluble gold complexes as catalysts for organic transformations [1]. Although a number of synthetically useful transformations have been developed, gold complexes have demonstrated particular utility as catalysts for the functionalization of CÀC multiple bonds with heteroatom nucleophiles, including oxygen nucleophiles such as water, carbinols, carbonyl compounds, and ethers. Early efforts in this area focused primarily on the application of simple gold(III) salts as catalysts, but interest has increasingly shifted toward the application of cationic gold(I) complexes supported by a phosphine or N-heterocyclic carbene ligands as catalysts for CÀO bond formation. These cationic gold(I) complexes are electrophilic, highly carbophilic compounds that are particularly suitable for p-activation catalysis. Herein we review the application of soluble gold(I) and gold(III) complexes as catalysts for the addition of oxygen nucleophiles to CÀC multiple bonds through 2008. This review is restricted to transformations that involve addition of an oxygen nucleophile to an electronically unactivated CÀC multiple bond catalyzed by a well-defined, soluble gold species.

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Gold(I)‐Catalyzed Cycloisomerization of 3‐Methoxy‐1,6‐enynes Featuring Tandem Cyclization and [3,3]‐Sigmatropic Rearrangement

Cited by 102 publications

References 48 publications

Gold(I)-catalyzed Tandem Cyclization of 3-(tert-Butoxycarbonyloxy)-1,6-enynes

Gold(I)-catalyzed Tandem Cyclization of 3-(tert-Butoxycarbonyloxy)-1,6-enynes

Gold‐Catalyzed Migrations and Ring Expansions

Gold‐Catalyzed Addition of Oxygen Nucleophiles to CC Multiple Bonds

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