A Facile, Efficient and Selective Deprotection of P - Methoxy Benzyl Ethers Using Zinc (II) Trifluoromethanesulfonate

: Deprotection is significant and conducted over mild reaction conditions, in order to restrict any more side reactions with sensitive functional groups as well as racemization or epimerization of stereo center because the protective groups are often cleaved at last stage in the synthesis. P - Methoxy benzyl (PMB) ether appears unique due to its easy introduction and removal than the other benzyl ether protecting groups. A facile, efficient and highly selective cleavage of P - methoxy benzyl ethers was reported by using 20 mole% Zinc (II) Trifluoromethanesulfonate at room temperature in acetonitrile solvent over 15-120 min. time period. To study the generality of this methodology, several PMB ethers were prepared from a variety of substrates having different protecting groups and subjected to deprotection of PMB ethers using Zn(OTf)2 in acetonitrile. In this methodology, zinc triflate cleaves only PMB ethers without affecting acid sensitivity, base sensitivity and also chiral epoxide groups.

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Visible Light-Mediated Oxidative Debenzylation

10.26434/chemrxiv.13135814 ◽

2020 ◽

Author(s):

Cristian Cavedon ◽

Eric T. Sletten ◽

Amiera Madani ◽

Olaf Niemeyer ◽

Peter H. Seeberger ◽

...

Keyword(s):

Reaction Time ◽

Visible Light ◽

Functional Groups ◽

Continuous Flow ◽

Protecting Groups ◽

Benzyl Ether ◽

Complex Molecules ◽

Protective Groups ◽

Benzyl Ethers ◽

Harsh Conditions

Protecting groups are key in the synthesis of complex molecules such as carbohydrates to distinguish functional groups of similar reactivity. The harsh conditions required to cleave stable benzyl ether protective groups are not compatible with many other protective and functional groups. The mild, visible light-mediated debenzylation disclosed here renders benzyl ethers orthogonal protective groups. Key to success is the use of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as stoichiometric or catalytic photooxidant such that benzyl ethers can be cleaved in the presence of azides, alkenes, and alkynes. The reaction time for this transformation can be reduced from hours to minutes in continuous flow. <br>

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One-Pot, Metal-Free Synthesis of Dimethyl Carbonate from CO2 at Room Temperature

Sustainable Chemistry ◽

10.3390/suschem1030020 ◽

2020 ◽

Vol 1 (3) ◽

pp. 298-314

Author(s):

Santosh Govind Khokarale ◽

Thai Q. Bui ◽

Jyri-Pekka Mikkola

Keyword(s):

Ionic Liquid ◽

Room Temperature ◽

Dimethyl Carbonate ◽

High Selectivity ◽

Chemical Species ◽

Side Reactions ◽

Ambient Conditions ◽

Reaction Conditions ◽

One Pot ◽

Metal Free

Herein, we report on the metal-free, one-pot synthesis of industrially important dimethyl carbonate (DMC) from molecular CO2 under ambient conditions. In this process, initially the CO2 was chemisorbed through the formation of a switchable ionic liquid (SIL), [DBUH] [CH3CO3], by the interaction of CO2 with an equivalent mixture of organic superbase 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) and methanol. The obtained SIL further reacted with methyl iodide (CH3I) to form DMC. The synthesis was carried out in both dimethyl sulfoxide (DMSO) and methanol. Methanol is preferred, as it not only served as a reagent and solvent in CO2 capture and DMC synthesis, but it also assisted in controlling the side reactions between chemical species such as CH3I and [DBUH]+ cation and increased the yield of DMC. Hence, the use of methanol avoided the loss of captured CO2 and favored the formation of DMC with high selectivity. Under the applied reaction conditions, 89% of the captured CO2 was converted to DMC. DBU was obtained, achieving 86% recovery of its salts formed during the synthesis. Most importantly, in this report we describe a simple and renewable solvent-based process for a metal-free approach to DMC synthesis under industrially feasible reaction conditions.

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Visible Light-Mediated Oxidative Debenzylation

10.26434/chemrxiv.13135814.v1 ◽

2020 ◽

Author(s):

Cristian Cavedon ◽

Eric T. Sletten ◽

Amiera Madani ◽

Olaf Niemeyer ◽

Peter H. Seeberger ◽

...

Keyword(s):

Reaction Time ◽

Visible Light ◽

Functional Groups ◽

Continuous Flow ◽

Protecting Groups ◽

Benzyl Ether ◽

Complex Molecules ◽

Protective Groups ◽

Benzyl Ethers ◽

Harsh Conditions

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Naturally Occurring Organic Acid-catalyzed Facile Diastereoselective Synthesis of Biologically Active (E)-3-(arylimino)indolin-2-one Derivatives in Water at Room Temperature

Current Organic Chemistry ◽

10.2174/1385272822666190924182538 ◽

2019 ◽

Vol 23 (16) ◽

pp. 1778-1788 ◽

Cited By ~ 5

Author(s):

Gurpreet Kaur ◽

Arvind Singh ◽

Kiran Bala ◽

Mamta Devi ◽

Anjana Kumari ◽

...

Keyword(s):

Room Temperature ◽

Biologically Active ◽

Environmentally Benign ◽

Diastereoselective Synthesis ◽

Substituted Anilines ◽

Reaction Conditions ◽

Naturally Occurring ◽

Acid Catalyzed ◽

Reaction Media ◽

Column Chromatographic

A simple, straightforward and efficient method has been developed for the synthesis of (E)-3-(arylimino)indolin-2-one derivatives and (E)-2-((4-methoxyphenyl)imino)- acenaphthylen-1(2H)-one. The synthesis of these biologically-significant scaffolds was achieved from the reactions of various substituted anilines and isatins or acenaphthaquinone, respectively, using commercially available, environmentally benign and naturally occurring organic acids such as mandelic acid or itaconic acid as catalyst in aqueous medium at room temperature. Mild reaction conditions, energy efficiency, good to excellent yields, environmentally benign conditions, easy isolation of products, no need of column chromatographic separation and the reusability of reaction media are some of the significant features of the present protocol.

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One-pot Synthesis of Pyrazolone Sulfones by Iodine-catalyzed Sulfenylation of Pyrazolones with Aryl Sulfonyl Hydrazides Followed by Oxidation in Water

Current Organic Synthesis ◽

10.2174/1570179414666171020113745 ◽

2018 ◽

Vol 15 (3) ◽

pp. 380-387

Author(s):

Xia Zhao ◽

Xiaoyu Lu ◽

Lipeng Zhang ◽

Tianjiao Li ◽

Kui Lu

Keyword(s):

Double Bond ◽

Efficient Method ◽

Room Temperature ◽

Sulfonyl Chloride ◽

Antibacterial Activities ◽

Oxidation Reactions ◽

Reaction Conditions ◽

One Pot ◽

X Ray ◽

Amide Form

Aim and Objective: Pyrazolone sulfones have been reported to exhibit herbicidal and antibacterial activities. In spite of their good bioactivities, only a few methods have been developed to prepare pyrazolone sulfones. However, the substrate scope of these methods is limited. Moreover, the direct sulfonylation of pyrazolone by aryl sulfonyl chloride failed to give pyrazolone sulfones. Thus, developing a more efficient method to synthesize pyrazolone sulfones is very important. Materials and Method: Pyrazolone, aryl sulphonyl hydrazide, iodine, p-toluenesulphonic acid and water were mixed in a sealed tube, which was heated to 100°C for 12 hours. The mixture was cooled to 0°C and m-CPBA was added in batches. The mixture was allowed to stir for 30 min at room temperature. The crude product was purified by silica gel column chromatography to afford sulfuryl pyrazolone. Results: In all cases, the sulfenylation products were formed smoothly under the optimized reaction conditions, and were then oxidized to the corresponding sulfones in good yields by 3-chloroperoxybenzoic acid (m-CPBA) in water. Single crystal X-ray analysis of pyrazolone sulfone 4aa showed that the major tautomer of pyrazolone sulfones was the amide form instead of the enol form observed for pyrazolone thioethers. Moreover, the C=N double bond isomerized to form an α,β-unsaturated C=C double bond. Conclusion: An efficient method to synthesize pyrazolone thioethers by iodine-catalyzed sulfenylation of pyrazolones with aryl sulfonyl hydrazides in water was developed. Moreover, this method was employed to synthesize pyrazolone sulfones in one-pot by subsequent sulfenylation and oxidation reactions.

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Lithium-mediated Ferration of Fluoroarenes

CHIMIA International Journal for Chemistry ◽

10.2533/chimia.2020.866 ◽

2020 ◽

Vol 74 (11) ◽

pp. 866-870

Author(s):

Lewis C. H. Maddock ◽

Alan Kennedy ◽

Eva Hevia

Keyword(s):

Hydrogen Atom ◽

Organometallic Chemistry ◽

Room Temperature ◽

Structural Elucidation ◽

Side Reactions ◽

Metal Base ◽

Lithium Amide ◽

Mixed Metal ◽

Important Challenge

While fluoroaryl fragments are ubiquitous in many pharmaceuticals, the deprotonation of fluoroarenes using organolithium bases constitutes an important challenge in polar organometallic chemistry. This has been widely attributed to the low stability of the in situ generated aryl lithium intermediates that even at –78 °C can undergo unwanted side reactions. Herein, pairing lithium amide LiHMDS (HMDS = N{SiMe3}2) with FeII(HMDS)2 enables the selective deprotonation at room temperature of pentafluorobenzene and 1,3,5-trifluorobenzene via the mixed-metal base [(dioxane)LiFe(HMDS)3] (1) (dioxane = 1,4-dioxane). Structural elucidation of the organometallic intermediates [(dioxane)Li(HMDS)2Fe(ArF)] (ArF = C6F5, 2; 1,3,5-F3-C6H2, 3) prior electrophilic interception demonstrates that these deprotonations are actually ferrations, with Fe occupying the position previously filled by a hydrogen atom. Notwithstanding, the presence of lithium is essential for the reactions to take place as Fe II (HMDS)2 on its own is completely inert towards the metallation of these substrates. Interestingly 2 and 3 are thermally stable and they do not undergo benzyne formation via LiF elimination.

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Rh(III)-Catalyzed Olefination and Alkylation of Arenes with Maleimides: A Tunable Strategy for C(sp2)–H Functionalization

Synthesis ◽

10.1055/s-0037-1610765 ◽

2021 ◽

Author(s):

Hongji Li ◽

Wenjie Zhang ◽

Xueyan Liu ◽

Zhenfeng Tian

Keyword(s):

Room Temperature ◽

Functional Group ◽

Reaction Conditions ◽

Bond Functionalization ◽

Alkylation Process ◽

Coupling Partner

AbstractWe herein report a new nitrogen-directed Rh(III)-catalyzed C(sp2)–H bond functionalization of N-nitrosoanilines and azoxybenzenes with maleimides as a coupling partner, in which the olefination/alkylation process can be finely controlled at room temperature by variation of the reaction conditions. This method shows excellent functional group tolerance, and presents a mild access to the resulting olefination/alkylation products in moderate to good yields.

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Understanding Sulfur Redox Mechanisms in Different Electrolytes for Room-Temperature Na–S Batteries

Nano-Micro Letters ◽

10.1007/s40820-021-00648-w ◽

2021 ◽

Vol 13 (1) ◽

Author(s):

Hanwen Liu ◽

Wei-Hong Lai ◽

Qiuran Yang ◽

Yaojie Lei ◽

Can Wu ◽

...

Keyword(s):

Room Temperature ◽

High Surface ◽

Reversible Capacity ◽

High Loading ◽

Side Reactions ◽

Liquid Sulfur ◽

Shuttle Effect ◽

Loading Ratio ◽

Solid Liquid ◽

Sulfur Cathodes

Abstract This work reports influence of two different electrolytes, carbonate ester and ether electrolytes, on the sulfur redox reactions in room-temperature Na–S batteries. Two sulfur cathodes with different S loading ratio and status are investigated. A sulfur-rich composite with most sulfur dispersed on the surface of a carbon host can realize a high loading ratio (72% S). In contrast, a confined sulfur sample can encapsulate S into the pores of the carbon host with a low loading ratio (44% S). In carbonate ester electrolyte, only the sulfur trapped in porous structures is active via ‘solid–solid’ behavior during cycling. The S cathode with high surface sulfur shows poor reversible capacity because of the severe side reactions between the surface polysulfides and the carbonate ester solvents. To improve the capacity of the sulfur-rich cathode, ether electrolyte with NaNO3 additive is explored to realize a ‘solid–liquid’ sulfur redox process and confine the shuttle effect of the dissolved polysulfides. As a result, the sulfur-rich cathode achieved high reversible capacity (483 mAh g−1), corresponding to a specific energy of 362 Wh kg−1 after 200 cycles, shedding light on the use of ether electrolyte for high-loading sulfur cathode.

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Process intensification for enzyme assisted turmeric starch hydrolysis in hydrotropic and supercritical conditions

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2020-0161 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Yogita P. Labrath ◽

Prafulla V. Belge ◽

Uma G. Kulkarni ◽

Vilas G. Gaikar

Keyword(s):

Residence Time ◽

Filtration Rate ◽

Room Temperature ◽

Curcuma Longa ◽

Process Intensification ◽

Enzyme Treatment ◽

Starch Hydrolysis ◽

Reaction Conditions ◽

Natural Form ◽

Hydrolysis Of

Abstract The turmeric rhizome (Curcuma longa) contains curcuminoids embedded in the starch matrix. It is thus important to target starch hydrolysis to enhance extraction of curcuminoids. In the case of starch hydrolysis, α-amylase is more efficient when the starch is in a gelatinised form than when it is in its natural form. The present work includes hydrolysis of turmeric starch in its natural and gelatinised forms using α-amylase in hydrotrope solution (HS) and scCO2. The optimum rate of starch hydrolysis was obtained using 200 IU cm−3 of α-amylase, at reaction conditions of 6.5 pH at 328 K when 10% w/w of turmeric powder was stirred at 900 rpm in HSs. The hydrolysis in 15 MPa scCO2 at room temperature required a phase modifier and 40 min of residence time (RT). The enzyme treatment of turmeric powder in HSs increased the filtration rate for curcuminoid extraction (gelatinised and native) compared to untreated turmeric powder.

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Bu4N+-Controlled Addition and Olefination with Ethyl 2-(Trimethylsilyl)acetate via Silicon Activation

Synlett ◽

10.1055/s-0036-1588805 ◽

2017 ◽

Vol 28 (18) ◽

pp. 2401-2406 ◽

Cited By ~ 2

Author(s):

Donal O’Shea ◽

Manas Das ◽

Atul Manvar ◽

Ian Fox ◽

Dilwyn Roberts

Keyword(s):

Room Temperature ◽

Product Formation ◽

Unsaturated Ester ◽

Reaction Conditions ◽

Diverse Range ◽

Inorganic Cation ◽

Tetrabutyl Ammonium ◽

Aldehydes And Ketones ◽

Subsequent Elimination ◽

Hydroxy Esters

Catalytic Bu4NOAc as silicon activator of ethyl 2-(trimethylsilyl)acetate, in THF, was utilized for the synthesis of β-hydroxy esters, whereas employing catalytic Bu4NOTMS gave α,β-unsaturated esters. The established reaction conditions were applicable to a diverse range of aromatic, heteroaromatic, aliphatic aldehydes and ketones. Reactions were achieved at room temperature without taking any of the specialized precautions that are in place for other organometallics. A stepwise olefination pathway via silylated β-hydroxy esters with subsequent elimination to form the α,β-unsaturated ester has been demonstrated. The key to selective product formation lies in use of the weaker acetate activator which suppresses subsequent elimination whereas stronger TMSO– activator (and base) facilitates both addition and elimination steps. The use of tetrabutyl ammonium salts for both acetate and trimethylsilyloxide activators provide enhanced silicon activation when compared to their inorganic cation counterparts.

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