[2+2] Cycloaddition of ketenes with ynamides. A general method for the synthesis of 3-aminocyclobutenone derivatives

Kohnen, Amanda L.; Mak, Xiao Yin; Lam, Tin Yiu; Dunetz, Joshua R.; Danheiser, Rick

doi:10.1016/j.tet.2005.11.088

Cited by 55 publications

(69 citation statements)

References 44 publications

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“…16 We investigated the coupling of BnNHCO 2 Me with 1-bromo-2-phenylacetylene in some detail in an attempt to identify the experimental variables that might be responsible for Tam's inability to reproduce our results and the results of Hsung and co-workers. 11 We obtained the expected ynamide 11 in 63% yield using our method (Table 1, entry 7), and in 79% yield by employing the "second-generation" procedure of Hsung. In our experience, both methods have proved to be highly reproducible.…”

Section: Discussionmentioning

confidence: 90%

Synthesis of Ynamides by N ‐Alkynylation of Amine Derivatives. Preparation of N ‐Allyl‐ N ‐(Methoxycarbonyl)‐1,3‐Decadiynylamine

Kohnen¹,

Dunetz²,

Danheiser

2006

Organic Syntheses

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A 250-mL, three-necked, round-bottomed flask equipped with a magnetic stir bar, an argon gas inlet tube, a rubber septum, which is pierced with a Teflon-coated thermocouple, and a 200-mL pressure-equalizing addition funnel fitted with a rubber septum (Note 2) is charged via syringe through the septum with allylamine (1) (14.0 mL, 10.68 g, 187 mmol, 2.1 equiv) (Note 3) and 100 mL of dichloromethane (Note 4). The solution is cooled to 0 °C (internal temperature) in an ice-water bath and a solution of methyl chloroformate (7.0 mL, 8.6 g, 91 mmol) (Note 5) in 30 mL of dichloromethane is added dropwise via the addition funnel over 10 min. The resulting white mixture is allowed to warm to room temperature over 30 min and then transferred to a 500-mL separatory funnel and extracted with 50 mL of aqueous 1M HCl solution, 50 mL of saturated aqueous NaHCO 3 solution, and 50 mL of saturated aqueous NaCl solution. The organic phase is dried over MgSO 4 , filtered, and concentrated by rotary evaporation (23 °C, 16 mmHg) to afford 10.12-10.26 g (97-98%) of carbamate 2 as a colorless oil (Note 6).Checked by Scott E. Denmark and Xiaorong Liu. 1 t-Butyl and ethyl N-allylcarbamate are commercially available. The method described here for the synthesis of the methyl derivative 2 illustrates a general procedure for the preparation of carbamates which usually delivers the desired compounds in near-quantitative yield and in a state of high purity, suitable for use in the N-alkynylation reaction without further purification. 2 The apparatus was flame-dried under reduced pressure (0.08 mmHg) and then maintained under an atmosphere of argon during the course of the reaction. 3 Allylamine (98%) was purchased from Alfa Aesar and used without purification. 4 Dichloromethane was purified by pressure filtration under argon through activated alumina. 5 Methyl chloroformate (99%) was obtained from Aldrich Chemical Company, Inc. and used as received. NIH Public Access

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Section: Discussionmentioning

confidence: 90%

Synthesis of Ynamides by N ‐Alkynylation of Amine Derivatives. Preparation of N ‐Allyl‐ N ‐(Methoxycarbonyl)‐1,3‐Decadiynylamine

Kohnen¹,

Dunetz²,

Danheiser

2006

Organic Syntheses

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“…A 8-mL resealable tube fitted with a rubber septum and argon inlet needle was charged with ynamide 24 xii (0.089 g, 0.50 mmol, 1.0 equiv), cyclobutenone 35 xviii (0.067 g, 0.54 mmol, 1.2 equiv) and 0.5 mL of toluene. The reaction mixture was heated at reflux for 1 h, then cooled to rt and concentrated to 0.254 g yellow oil.…”

Section: Experimental Procedures For Benzannulationsmentioning

confidence: 99%

Synthesis of Polycyclic Benzofused Nitrogen Heterocycles via a Tandem Ynamide Benzannulation/Ring-Closing Metathesis Strategy. Application in a Formal Total Synthesis of (+)-FR900482

2011

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A two-stage "tandem strategy" for the synthesis of benzofused nitrogen heterocycles is described that is particularly useful for the construction of systems with a high level of substitution on the benzenoid ring. The first stage in the strategy involves a benzannulation based on the reaction of cyclobutenones with ynamides. This cascade process proceeds via a sequence of four pericyclic reactions and furnishes a multiply substituted aniline derivative which can bear a variety of functionalized substituents at the position ortho to the nitrogen. In the second stage of the tandem strategy, ring closing metathesis generates the nitrogen heterocyclic ring. This two-step sequence provides efficient access to highly substituted dihydroquinolines, benzazepines, benzazocines, and related benzofused nitrogen heterocyclic systems. The application of this chemistry in a concise formal total synthesis of the anticancer agents (+)-FR900482 and (+)-FR66979 is described.

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“…This homo-[2+2]-cycloaddition gave di-arylated cyclobutenone 11 . 14 Upon further heating, cyclobutenone 11 underwent a tandem retro-4π/6π electrocyclization to generate 1,3-dihydroxyl naphthalene 13 in high yield. This transformation is reminiscent of the Danheiser benzannulation, in which vinylated cyclobutenones undergo a retro-4π and subsequent 6π electrocyclization to generate highly substituted aromatic rings.…”

Section: Introductionmentioning

confidence: 99%

A Concise Total Synthesis of Dictyodendrins F, H, and I Using Aryl Ynol Ethers as Key Building Blocks

Zhang

Ready

2016

J. Am. Chem. Soc.

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We report a concise total synthesis of dictyodendrin F and the first total syntheses of dictyodendrins H and I in six steps. In these syntheses, aryl ynol ethers were employed as the key building blocks to introduce aryl and heteroaryl rings in the dictyodendrins. This rapid synthesis utilized a novel hetero-[2+2]-cycloaddition reaction between two aryl ynol ethers to yield a cyclobutenone ring. The cyclobutenone was sequentially converted into a highly substituted carbazole via a retro-4π/6π-electrocyclization-N-acylation cascade reaction to provide the dictyodendrin core. Consecutive intramolecular oxidative coupling and deprotection gave dictyodendrins F, H, and I.

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[2+2] Cycloaddition of ketenes with ynamides. A general method for the synthesis of 3-aminocyclobutenone derivatives

Cited by 55 publications

References 44 publications

Synthesis of Ynamides by N ‐Alkynylation of Amine Derivatives. Preparation of N ‐Allyl‐ N ‐(Methoxycarbonyl)‐1,3‐Decadiynylamine

Synthesis of Ynamides by N ‐Alkynylation of Amine Derivatives. Preparation of N ‐Allyl‐ N ‐(Methoxycarbonyl)‐1,3‐Decadiynylamine

Synthesis of Polycyclic Benzofused Nitrogen Heterocycles via a Tandem Ynamide Benzannulation/Ring-Closing Metathesis Strategy. Application in a Formal Total Synthesis of (+)-FR900482

A Concise Total Synthesis of Dictyodendrins F, H, and I Using Aryl Ynol Ethers as Key Building Blocks

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