Hydrogen bonding in organic synthesis IV: A simple, high-yield method for the methylenation of catechols

Clark, James H.; Holland, Herbert L.; Miller, Jack M.

doi:10.1016/s0040-4039(00)93045-4

Cited by 87 publications

(34 citation statements)

References 5 publications

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“…This yielded two fractions which were than subjected to preparative TLC in CHCl 3 -hexane (8 : 2) to obtain irisoids B (2) Methylenation Reaction on 5 The relative positions of the methylenedioxy group and hydroxyl groups were confirmed by performing the methylenation reaction. 15) A solution of 5 (0.05 mol) in anhydrous DMF was shaken with anhydrous cesium fluoride (CsF) and then CH 2 Cl 2 (0.011 mol) was added to the solution. The reaction mixture was heated with stirring at 110-120°C for 1.5 h and then subjected to solvent-solvent extraction with diethylether and water.…”

Section: Methodsmentioning

confidence: 99%

“…The unreactivity of compound 5 with CH 2 Cl 2 in CsF and DMF confirmed the absence of two vicinal phenolic hydroxyl groups in 5. 15) Therefore the positions of hydroxyl groups in ring A were inferred at C-8 and C-11. The proton of C-8 OH appeared downfield at d 12.86 due to hydrogen bonding with C-7 carbonyl when the 1 H-NMR spectrum was recorded in C (1) 4641 (2) 2116 (1) 7949 (1) 41 (1) C (2) 6347 (3) 1700 (1) 8053 (2) 49 (1) C (3) 7401 (3) 1714 (1) 8965 (2) 53 (1) C (4) 6797 (3) 2139 (1) 9799 (2) 48 (1) C (4A)…”

Section: Benzopyrano-[32-c][2]-benzopyran-7(5h)-one Was Assigned To mentioning

confidence: 99%

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Five New Peltogynoids from Underground Parts of Iris bungei: A Mongolian Medicinal Plant.

Choudhary

Nur-E-Alam

Akhtar

et al. 2001

CHEMICAL & PHARMACEUTICAL BULLETIN

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Iris bungei MAXIM. (family Iridaceae) has been used in Mongolian traditional medicine for the treatment of various diseases, such as bacterial infections, cancer, and inflammation. Some benzoquinones isolated from Iris species have been used as anticancer agents in modern Chinese medicine.2,3) This paper describes the isolation and characterization of five new peltogynoids (1-5) from the underground parts of Iris bungei. Although peltogynoids have been isolated from several genera of the family Leguminosae, [4][5][6][7][8][9][10][11][12] this is the first report of the isolation of peltogynoids from the family Iridaceae and the first X-ray structure determination of peltogynoid-type compounds. Results and DiscussionThe methanolic extract of the underground parts of I. bungei was subjected to repeated column and preparative thin-layer chromatography to obtain compounds 1-5. Irisoid A (1) was isolated as a yellow amorphous powder. The highresolution electron impact mass spectrum (HREI-MS) of 1 showed the [M] ϩ at m/z 328.0597, in agreement with the molecular formula C 17 H 12 O 7 (Calcd 328.0583), indicating 12 degrees of unsaturation. Strong IR absorptions at 1652 (CϭO) and 1628 cm Ϫ1 (CϭC) along with UV bands at 350 (log e 3.93), 278 (log e 4.03), and 203 (log e 4.26) indicated that the compound has a flavone-type skeleton with oxygenation at the C-6a position.13) Typical fragment ions appeared in EI-MS at m/z 313, 182, and 146, indicating the presence of a methoxyl group at C-9 with two hydroxyl groups in ring A, and only one hydroxyl group in ring B (Fig. 1).The 1 H-NMR spectrum (C 5 D 5 N, 400 MHz) of 1 showed two sets of signals for a total of four aromatic protons, along with signals for one O-methylene and one methoxyl group (Table 1). This revealed the presence of two independent aromatic spin systems in the molecule. A singlet at d 6.98 corresponded to the H-11 of ring A. Three signals at d 7.19 (br d, J 2,3 ϭ8.3 Hz), 7.29 (dd, J 3,2 ϭ8.3 Hz and J 3,4 ϭ7.3 Hz) and 6.70 (br d, J 4,3 ϭ7.3 Hz) were assigned to the aromatic H-2, H-3, and H-4 protons, respectively. This assignment indicated the presence of substituents at C-1 and C-4a of the aromatic ring B. Two downfield methylene protons resonated as a singlet at d 5.13 (H-5), indicating the presence of an ethereal oxygen and aromatic moiety vicinal to the methylene carbon. A methoxyl methyl appeared as a singlet at d 3.93 substituted at C-9 of ring A. The appearance of a downfield singlet at d 12.82 when the 1 H-NMR was recorded in dimethyl sulfoxide (DMSO)-d 6 confirmed the presence of the OH group at C-8, which is involved in the hydrogen bonding with carbonyl group at C-7.The broad-band (BB) decoupled 13 C-NMR spectrum of 1 showed resonances for all 17 carbons in the molecule (Table 1). The audited distortionless enhancement by polarization transfer (ADEPT) spectrum revealed the presence of one methyl, one methylene, four methines, and 11 quaternary carbons. The carbonyl carbons appeared in the most downfielded region at d 175.4, whereas the other im...

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Section: Methodsmentioning

confidence: 99%

Section: Benzopyrano-[32-c][2]-benzopyran-7(5h)-one Was Assigned To mentioning

confidence: 99%

Five New Peltogynoids from Underground Parts of Iris bungei: A Mongolian Medicinal Plant.

Choudhary

Nur-E-Alam

Akhtar

et al. 2001

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…Compound 9 was subjected to alkylation using 1,2 dibromoethane in DMSO resulting in dioxane fused BTBT 2 which was purified by vacuum sublimation. O‐Alkylation of 9 by adapting a modified protocol using CsF and dibromomethane in DMF was attempted to synthesize 3 in 40 % yield (after vacuum sublimation). Starting from compound 4 , the overall yield of 2 and 3 were 12 % and 15 % respectively.…”

Section: Resultsmentioning

confidence: 99%

Oxacycle‐Fused [1]Benzothieno[3,2‐b][1]benzothiophene Derivatives: Synthesis, Electronic Structure, Electrochemical Properties, Ionisation Potential, and Crystal Structure

et al. 2018

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The molecular properties of [1]benzothieno[3,2‐b][1]benzothiophene (BTBT) are vulnerable to structural modifications, which in turn are determined by the functionalization of the backbone. Hence versatile synthetic strategies are needed to discover the properties of this molecule. To address this, we have attempted heteroatom (oxygen) functionalization of BTBT by a concise and easily scalable synthesis. Fourfold hydroxy‐substituted BTBT is the key intermediate, from which the compounds 2,3,7,8‐bis(ethylenedioxy)‐[1]benzothieno[3,2‐b][1]benzothiophene and 2,3,7,8‐bis(methylenedioxy)‐[1]benzothieno[3,2‐b][1]benzothiophene are synthesized. The difference in ether functionalities on the BTBT scaffold influences the ionisation potential values substantially. The crystal structure reveals the transformation of the herringbone motif in bare BTBT towards π‐stacked columns in the newly synthesized derivatives. The results are further justified by the simulated HOMO levels of the model compound.

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“…Total duration was 24 h. For direct HOESY experiments, the same mixing time (i.e. 1 s) and the same number of t 1 increments where used with 64 scans and a recycling delay of 10 s. Total duration was 24 h. The ND11 molecule was synthesized in our laboratory 28,29 with the help of Dr J.P. Joly and was dissolved in deuterated dimethyl sulfoxide at a final concentration of 0.5 M. The sample was carefully degassed by a sequence of 'freeze-pump-thaw' cycles, and the tube was subsequently sealed under vacuum. The cis-stilbene sample used in direct experiments is from Aldrich Chemicals, ref.…”

Section: Methodsmentioning

confidence: 99%

Heteronuclear Overhauser experiments for symmetric molecules

Walker¹,

Mutzenhardt²,

Canet³

2003

Magnetic Reson in Chemistry

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The nuclear Overhauser effect (NOE) arises from dipolar interactions between magnetic moments associated with nuclear spins and it has become a powerful tool to extract relevant pieces of structural information about small molecules, as well as in molecules of biological interest. As a consequence, accurate NOE measurement is a very crucial issue. Here, we present a comparison between direct and a new inverse HOESY experiment aimed at the detection of heteronuclear NOE between 1 H and 13 C, which is particularly well suited for symmetric compounds. It transpires that directly detected data are more suitable for quantitative assessment even if they suffer from lower sensitivity, whereas inverse detection is quite appropriate for a quick and qualitative assessment. In the latter experiment, unwanted cross-correlation effects may hide valuable NOE data (cross-relaxation), this drawback can be circumvented by a slight modification of the pulse sequence.

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Hydrogen bonding in organic synthesis IV: A simple, high-yield method for the methylenation of catechols

Cited by 87 publications

References 5 publications

Five New Peltogynoids from Underground Parts of Iris bungei: A Mongolian Medicinal Plant.

Five New Peltogynoids from Underground Parts of Iris bungei: A Mongolian Medicinal Plant.

Oxacycle‐Fused [1]Benzothieno[3,2‐b][1]benzothiophene Derivatives: Synthesis, Electronic Structure, Electrochemical Properties, Ionisation Potential, and Crystal Structure

Heteronuclear Overhauser experiments for symmetric molecules

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