Cationic Cyclopentannelation of Allene Ethers

Tius, Marcus A.

doi:10.1021/ar0200394

Cited by 226 publications

(150 citation statements)

References 25 publications

Supporting

Mentioning

148

Contrasting

Unclassified

Order By: Relevance

“…[1][2][3][4][5][6][7][8][9] The Nazarov reaction is often catalyzed by a Brønsted-or Lewis acid; coordination of which generates the requisite oxyallyl cation 2, which undergoes a stereospecific 4π-electron-5-atom electrocyclization to generate the C-C bond. Electrocyclization reactions are powerful transformations in organic synthesis that have been exploited to construct new C-C and new C-N bonds in a stereospecific manner.…”

Section: Introductionmentioning

confidence: 99%

“…[34][35][36][37][38][39][40] The most common approach is to intercept this intermediate with a nucleophile before deprotonation or elimination occurs. The resulting oxyallyl cation 25 triggers a [1,2] methyl shift to produce the more stable allylic cation 26. 35 They reported that exposure of divinyl ketone 9 to TiCl 4 produced 11 through the cationic olefin polycyclization of oxyallyl produces pentadienyl cation 24, which undergoes a 4π-electron-5-atom-electrocyclization.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Assembly of functionalized carbocycles or N-heterocycles through a domino electrocyclization–[1,2] migration reaction sequence

Jana

Driver

2015

Org. Biomol. Chem.

View full text Add to dashboard Cite

The development of processes that streamline the synthesis of complex, functionalized carbocycles and heterocycles remains a hotly pursued topic because their scaffolds are present in a range of bioactive molecules and electronic materials. Although the Nazarov reaction has emerged to be useful in the synthesis of carbocycles and heterocycles, using an electrocyclization to trigger a migration remains underdeveloped. By constructing several bonds in one operation, domino reaction sequences are particularly effective at improving the efficiency of synthesis. The use of transition metal catalysts has the potential to render these processes stereoselective. This review examines the use of electrocyclization-[1,2] migrations to construct molecules and is organized by the type of ring constructed and the order of the two steps in this process.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Assembly of functionalized carbocycles or N-heterocycles through a domino electrocyclization–[1,2] migration reaction sequence

Jana

Driver

2015

Org. Biomol. Chem.

View full text Add to dashboard Cite

show abstract

“…6 In the search for additional approaches toward rapid access to functionalized allenes for the intended [3+2] cycloaddition, we found that allenyl MOM ether, upon R deprotonation, has been used to prepare electron-rich allene derivatives en route to functional structures. 7 To our surprise, no study of these readily available, functionalized allenes in the presence of Au catalyst has been reported.…”

mentioning

confidence: 99%

“…In general, AcOH was the preferred proton source, and the reactions proceeded well at 0°C. For example, without purification of intermediate TMS ethers, 1-acetylcycloalkenes of different ring sizes underwent smooth reactions, and the cis-fused bicyclic ketones were formed in excellent yields (entries [6][7][8]. Notably, phenyl enone 5i participated in this two-step reaction as well, albeit in a low yield (entry 9).…”

mentioning

confidence: 99%

Two-Step Formal [3+2] Cycloaddition of Enones/Enals and Allenyl MOM Ether: Gold-Catalyzed Highly Diastereoselective Synthesis of Cyclopentanone Enol Ether Containing an All-Carbon Quaternary Center

2007

View full text Add to dashboard Cite

Five-membered carbocycles are of primary importance in organic synthesis, but their synthesis via modular and flexible 1,3-dipolar cycloaddition is hampered by the difficulty accessing all-carbon 1,3-dipoles. Various precursors or synthetic equivalents for the C 3 unit have been developed, 1 but there is still much need to expand their scope and develop new methods leading to highly efficient and stereoselective cycloadditions.Au catalysts have recently been shown as powerful soft Lewis acids in activating alkynes and allenes toward nucleophilic attack. 2 The alkenylgold intermediate generated can behave as an R-deprotonated gold carbenoid via resonance, reminiscent of an enolate, leading to novel reactivities (Scheme 1a). 3 We speculate that allene, if not immediately attacked by nucleophile upon Au activation, would become all-carbon 1,3-dipole A via resonance (Scheme 1b) and participate in concerted 1,3-dipolar cycloaddition. Herein, we disclose our study of this previously unknown concept and report an efficient two-step synthesis of cyclopentanone enol ethers containing an all-carbon quaternary center. An intramolecular [3+2] cycloaddition using allene as 1,3-dipole precursor 4 is proposed, supported by the observed excellent diastereoselectivity.While various useful Au-catalyzed reactions of allenes 5 have been developed, the allene substrates are usually without heteroatom directly attached to the 1,2-diene moiety, and their preparations often require multiple steps. We previously developed an in situ generation of carboxyallenes via Au-catalyzed rearrangement of propargylic esters, which substantially facilitated studies of the chemistry of these functionalized allenes with the very same Au catalyst while avoiding the difficulty in their preparation. 6 In the search for additional approaches toward rapid access to functionalized allenes for the intended [3+2] cycloaddition, we found that allenyl MOM ether, upon R deprotonation, has been used to prepare electron-rich allene derivatives en route to functional structures. 7 To our surprise, no study of these readily available, functionalized allenes in the presence of Au catalyst has been reported.We began with allenyl carbinol 1, prepared from cyclohex-1-enecarbaldehyde and allenyl MOM ether in one step (Scheme 2). Compound 1 contains an alkene and an electron-rich allene in close proximity and is ideal for studying Au-catalyzed [3+2] cycloaddition. Gratifyingly, treatment of 1 with 5 mol % of dichloro-(pyridine-2-carboxylato)gold (4) 8 in CH 2 Cl 2 gave cyclopentanone enol ether 2 9 as the major product and the expected dihydrofuran 3. The formation of 2 can be rationalized as shown in Scheme 2. Hence, selective Au III activation of the enolic double bond of the allenyl ether moiety gives oxocarbenium B, which is in resonance with 1,3-dipole C; subsequent intramolecular 1,3-dipolar cycloaddition of C forms Au carbenoid D with a strained bicyclo[3.1.0]-hexane moiety, 10 of which the cyclopropane ring is fragmented with the assistance of the OH group; the f...

show abstract

“…Allenes are versatile and valuable substructures in synthetic organic chemistry due to their characteristic structure and reactivity originated from the contiguous C¼C double bonds [25,26]. In particular, the axial chirality of allene derivatives has attracted much attention from organic chemists from the viewpoint of synthetic utility as chiral synthons.…”

Section: Isomerization Of Alkynoates To Allenoatesmentioning

confidence: 99%

Bifunctional Guanidines as Hydrogen-Bond-Donating Catalysts

Kobayashi

Takemoto

2015

Topics in Heterocyclic Chemistry

View full text Add to dashboard Cite

Bicyclic guanidines, bearing 2-aminoquinazolin-4-one and 3-aminobenzothiadiazine-1,1-dioxide core structures, work as bifunctional amine catalysts, due to a double hydrogen-bond-donating ability of two guanidine N-H protons, which are capable of activating both nucleophile and electrophile simultaneously. In fact, these guanidine catalysts revealed to promote several asymmetric reactions such as hydrazination of active methylene compounds with azodicarboxylate and 1,3-proton migration of alkynoates to allenoates as well as the oxa-Michael addition and epoxidation of α,β-unsaturated amides and esters with better chemical yields and higher enantioselectivities than the corresponding thioureas. The catalytic mechanisms of these asymmetric reactions and their synthetic applications for biologically active molecules are also discussed in this chapter.

show abstract

Cationic Cyclopentannelation of Allene Ethers

Cited by 226 publications

References 25 publications

Assembly of functionalized carbocycles or N-heterocycles through a domino electrocyclization–[1,2] migration reaction sequence

Assembly of functionalized carbocycles or N-heterocycles through a domino electrocyclization–[1,2] migration reaction sequence

Two-Step Formal [3+2] Cycloaddition of Enones/Enals and Allenyl MOM Ether: Gold-Catalyzed Highly Diastereoselective Synthesis of Cyclopentanone Enol Ether Containing an All-Carbon Quaternary Center

Bifunctional Guanidines as Hydrogen-Bond-Donating Catalysts

Contact Info

Product

Resources

About