Electrochemical vicinal oxyazidation of α-arylvinyl acetates

• Yi-Lun Li,
• Zhaojiang Shi,
• Tao Shen and
• Ke-Yin Ye

Beilstein J. Org. Chem. 2022, 18, 1026–1031, doi:10.3762/bjoc.18.103

• diverse α-azidoketones in good yields without the use of a stoichiometric amount of chemical oxidant. A range of functionality is shown to be compatible with this transformation, and further applications are demonstrated. Keywords: azide; azidoketone; electrosynthesis; enol acetate; radical

• ), and benzofuran (23) were all amenable in this transformation. In addition, various linear- (24, 25) and cyclic enol acetates (26, 27) also readily underwent the anticipated oxyazidation. Unfortunately, the current protocol was not applicable to the oxyazidation of enol acetate deriving from aliphatic

• ). The enol acetate A first undergoes anodic oxidation to form a radical cation intermediate B, which is then intercepted by azidotrimethylsilane to afford the benzyl radical C. Subsequently, this radical is further anodically oxidized to its oxocarbenium ion intermediate D, which finally reacts with

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

• , active methylene compounds, and a conjugated enol acetate of a steroid were all fluorinated in moderate to high yields. The fluorination of anisole required high temperature and neat conditions suggesting that the fluorination power of 20-2 is not so high. 1-21. Perfluoro[N-fluoro-N-(4-pyridyl)acetamide

Thiol-free chemoenzymatic synthesis of β-ketosulfides

• Adrián A. Heredia,
• Martín G. López-Vidal,
• Marcela Kurina-Sanz,
• Fabricio R. Bisogno and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2019, 15, 378–387, doi:10.3762/bjoc.15.34

• h was achieved by a twofold increase of lipase loading (Table 2, entry 13). On the contrary, no conversion was detected for the α,β-diphenyl enol acetate substrate 1q (Table 2, entry 17). In order to test the chemoselectivity of the enzymatic hydrolysis, we turned our attention to the acyl moiety of

• , considering the high steric demand of α- and ß-substituents. For even bulkier S-(bromobenzodioxole)methyl derivative 1t (Table 2, entry 20) no conversion was detected at 24 h. Similar results were obtained with the S-propyl-3-phthalimido derivative 1u (Table 2, entry 21) and the dimeric substrate bis-enol

• acetate 1p (Table 2, entry 16), suggesting that o-iodobenzyl substituent is approaching the upper limit of steric congestion. Additional β-substitution could be tolerated in the tetralone-derived substrate, 1m, affording 52 and 65% conversion at 24 and 48 h, respectively. Accordingly, 95% conversion at 24

Investigation of the electrophilic reactivity of the biologically active marine sesquiterpenoid onchidal and model compounds

• Melissa M. Cadelis and
• Brent R. Copp

Beilstein J. Org. Chem. 2018, 14, 2229–2235, doi:10.3762/bjoc.14.197

• dialdehyde 11 with dialdehyde 12 (1:1). Attempts at chromatographic separation of these two isomers resulted in degradation of 12. Final conversion of 11 to enol acetate 13 was achieved by overnight reaction with pyridine and acetic anhydride. Purification by silica gel column chromatography afforded the

• desired E,E enol acetate 13 in 17% yield. A lack of purified dialdehyde 12 prevented any attempt at the preparation of enolacetate 14. Having developed a successful synthetic route to n-pentyl side-chain dialdehyde 11 and enol acetate 13, the synthesis of analogues 15–18 with a side-chain more comparable

• and 26 with LiAlH4 afforded the corresponding diols 27 and 28 in 61% and 71% yield, respectively, which upon oxidation (DMP) afforded dialdehydes 15 and 16 in 49% and 73% yield, respectively. The reaction of dialdehyde 15 with Ac2O and pyridine afforded enol acetate 17 in 43% yield after purification

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• enol-acetate with NBS led to 277, which was heated in water–dioxane at 100 °C to give 7-hydroxy-2,3-benzotropone (241) by an elimination process. Galantay’s group also reported the synthesis of 7-hydroxy-2,3-benzotropone (241), which was similar to the synthesis of 2-hydroxy-4,5-benzotropone (238) as

• studies for 241A and 241B [177]. 5.4. 4-Hydroxy-2,3-benzotropone (174) 5.4.1. Synthesis of 4-hydroxy-2,3-benzotropone (174): Benzotropolone 174 was prepared through intermediate bis-enol acetate obtained from reaction between benzo[7]annulene-3,7-dione (300) and isopropenyl acetate followed by

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• yields were moderate to poor. In particular, enol acetate 1b, prepared from symmetrical undecan-6-one, gave a mixture of the desired α-CF3 ketone and two isomeric enol acetates 1b'. In 2014, Li, Duan and co-workers applied the conditions described by Langlois to a series of enol acetates 3 derived from

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• and Smith [219][220]. The synthesis of the cyclization precursors started from enynes like 297, beginning with cis-selective Rieke-Zn reduction. Epoxidation followed by oxidation furnished cis-vinylketone-epoxide 298. Enolate formation and acetate trapping afforded an intermediate enol-acetate, which

Diastereoselectivity in the Staudinger reaction of pentafluorosulfanylaldimines and ketimines

• Alexander Penger,
• Cortney N. von Hahmann,
• Alexander S. Filatov and
• John T. Welch

Beilstein J. Org. Chem. 2013, 9, 2675–2680, doi:10.3762/bjoc.9.303

• of SF5Cl to the enol ether 2 instead of the previously described additions to enol acetates [16] (Scheme 1). In earlier studies, it was found that the yield of SF5Cl addition to enol acetates was highly dependent upon the purity of the enol acetate substrate, compounds surprisingly difficult to

• purify. Since vinyl acetate is the only enol acetate readily accessible for this reaction, the commercial availability of high purity propenyl and butenyl ethers 2b and 2c rendered these starting materials highly attractive for the formation of SF5-bearing aldehydes. After addition of SF5Cl to 2

• imine 5 resulted only in decomposition. Excess amine 4 that was present was acylated by benzyloxyacetyl chloride to form the corresponding amide. The utility of the ketene–imine cyclization was not limited to aldimines. The addition of SF5Br to the enol acetate of ethyl pyruvate 9 formed ethyl

Continuous gas/liquid–liquid/liquid flow synthesis of 4-fluoropyrazole derivatives by selective direct fluorination

• Jessica R. Breen,
• Graham Sandford,
• Dmitrii S. Yufit,
• Judith A. K. Howard,
• Jonathan Fray and
• Bhairavi Patel

Beilstein J. Org. Chem. 2011, 7, 1048–1054, doi:10.3762/bjoc.7.120

• formation by base catalysis, by metal catalysis or by fluorination of appropriate pre-formed enol derivatives, such as trimethylsilyl enols or enol acetate derivatives [13][14]. Dicarbonyl systems are, of course, widely used for the construction of heterocyclic ring systems such a pyrimidine, pyridazine and

Do α-acyloxy and α-alkoxycarbonyloxy radicals fragment to form acyl and alkoxycarbonyl radicals?

• Dennis P. Curran and
• Tiffany R. Turner

Beilstein J. Org. Chem. 2006, 2, No. 10, doi:10.1186/1860-5397-2-10

• , but again only a trace of 15 (1%) was detected. These results suggest chain propagation problems at this concentration, which is near the dilution limit for typical radical chain reactions. The results for cyclization of enol acetate 11a at four different concentrations are shown in the lower part of