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Selective Synthesis of Acylated Cross-Benzoins from Acylals and Aldehydes via N-Heterocyclic Carbene Catalysis
The utility of acylals as building blocks for selective cross-benzoin synthesis was explored in this study. The synthesis of α-acetoxyketones (O-acyl cross-benzoins) was achieved via selective N-heterocyclic carbene-catalyzed cross-benzoin reactions using acylals as aldehyde equivalents. Thus, the combination of ortho-substituted phenyl acylals and aromatic/aliphatic aldehydes as coupling substrates using bicyclic triazolium salts as precatalysts and potassium carbonate as a base in THF at reflux temperature selectively yielded O-acyl cross-benzoins.
Onodera, Kou,Suzuki, Yumiko,Takashima, Ryo
supporting information
p. 4197 - 4202
(2021/06/27)

Application of poly(Vinylbenzyltrimethylammonium tribromide) resin as an efficient polymeric catalyst in the acetalization and diacetylation of benzaldehydes
The applications of a new supported tribromide reagent (poly(vinylbenzyltrimethylammonium tribromide) resin) were reported. This supported tribromide resin was used as a catalyst in the acetalization and diacetylation of benzaldehydes under mild conditions with high efficiency. The effects of solvents, and amount of the supported tribromide resin on the reactions were investigated. Under the optimal conditions, most of acetal and 1,1-diacetates of benzaldehydes were selectively obtained in excellent yields.
Han, Bingbing,Hu, Junjun,Li, Xianwei,Zheng, Zubiao
supporting information
p. 287 - 293
(2021/04/28)

Sustainable electrochemical decarboxylative acetoxylation of aminoacids in batch and continuous flow
Introduction of acetoxy groups to organic molecules is important for the preparation of many active ingredients and synthetic intermediates. A commonly used and attractive strategy is the oxidative decarboxylation of aliphatic carboxylic acids, which entails the generation of a new C(sp3)-O bond. This reaction has been traditionally carried out using excess amounts of harmful lead(iv) acetate. A sustainable alternative to stoichiometric oxidants is the Hofer-Moest reaction, which relies on the 2-electron anodic oxidation of the carboxylic acid. However, examples showing electrochemical acetoxylation of amino acids are scarce. Herein we present a general and scalable procedure for the anodic decarboxylative acetoxylation of amino acids in batch and continuous flow mode. The procedure has been applied to the derivatization of several natural and synthetic amino acids, including key intermediates for the synthesis of active pharmaceutical ingredients. Good to excellent yields were obtained in all cases. Transfer of the process from batch to a continuous flow cell signficantly increased the reaction throughput and space-time yield, with excellent product yields obtained even in a single-pass. The sustainability of the electrochemical protocol has been examined by evaluating its green metrics. Comparison with the conventional method demonstrates that an electrochemical approach has a significant positive effect on the greenness of the process.
K?ckinger, Manuel,Hanselmann, Paul,Roberge, Dominique M.,Geotti-Bianchini, Piero,Kappe, C. Oliver,Cantillo, David
supporting information
p. 2382 - 2390
(2021/04/12)

The studies on chemoselective promiscuous activity of hydrolases on acylals transformations
Chemoselective, mild and convenient protocol for the hydrolysis of the synthetically relevant acylals via promiscuous enzyme-catalyzed hydrolysis has been developed. It has been shown that promiscuous activity of the used hydrolases dominates their native activity related with carboxylic esters hydrolysis. The main advantage of the present methodology is that it can be conducted under neutral conditions at room temperature. Moreover, complete deprotection of acylals takes place within 10–20 min. Developed protocol can be used with compounds having a variety of hydrolytic labile groups since the cleavage is proceeded under neutral conditions and occurs exclusively on acylal moiety. Further this protocol was extended by the tandem Passerini multicomponent reaction leading to the α-acetoxy amides using acylals as the surrogates of the carbonyl components to P-MCR.
Koszelewski, Dominik,Ostaszewski, Ryszard
(2019/02/27)

Acylation of Phenols, Alcohols, Thiols, Amines and Aldehydes Using Sulfonic Acid Functionalized Hyper-Cross-Linked Poly(2-naphthol) as a Solid Acid Catalyst
Abstract: The hyper-cross-linked porous poly(2-naphthol) fabricated by the Friedel–Crafts alkylation of 2-naphthol has been functionalized with sulfonic acid to obtain a solid acid catalyst. The catalyst is applied for the protection of phenol, alcohols, thiols, amines and aldehydes with acetic anhydride at room temperature. The catalytic protection using the new solid acid is featured by achieving high yield at neat condition, needing no aqueous work-up and/or chromatographic separation, and showing excellent recycling efficiency, suggesting the potential of this sulfonated porous polymers as a new protection protocol in a wide range of sustainable chemical reactions. Graphical Abstract: [Figure not available: see fulltext.].
Kalla, Reddi Mohan Naidu,Reddy, Sirigireddy Sudharsan,Kim, Il
p. 2696 - 2705
(2019/05/28)

1,1-Diacyloxy-1-phenylmethanes as versatile N-acylating agents for amines
1,1-Diacyloxy-1-phenylmethanes and 1-pivaloxy-1-acyloxy-1-phenylmethanes have been used as bench stable N-acylating reagents for primary and secondary amines and anilines under solvent-free conditions to afford their corresponding amides in good yield.
Chapman, Robert. S.L.,Tibbetts, Joshua. D.,Bull, Steven. D.
p. 5330 - 5339
(2018/06/15)

N-Propylsulfamic acid supported onto magnetic Fe3O4 nanoparticles (MNPs-PSA) as a green and reusable heterogeneous nanocatalyst for the chemoselective preparation and deprotection of acylals
Abstract: N-propylsulfamic acid supported onto magnetic Fe3O4 nanoparticles (MNPs-PSA) was simply synthesized and used as a highly efficient, environmentally friendly, and chemoselective catalyst for the synthesis of 1,1-diacetates (acylals) from the one-pot condensation reaction of various aromatic aldehydes with acetic anhydride, in high yield of products (86–96%) and short reaction time (20–60?min) under solvent-free conditions at room temperature. In addition to these results, we further studied the possibility of deprotection of the resulting acylals into benzaldehyde derivatives in this catalytic system by the addition of water. More importantly, noteworthy advantages of this study are non-use of toxic organic solvents and catalysts, simple work-up procedure, short reaction time, high yield of products, and recovery and reusability of MNPs-PSA by an external magnet. Graphical Abstract: A simple and highly efficient procedure for the protection of various aldehydes with acetic anhydride in the presence of N-propylsulfamic acid supported onto magnetic Fe3O4 nanoparticles (MNPs-PSA) is reported. We further studied the possibility of deprotection of the resulting acylals into benzaldehyde derivatives in this catalytic system by the addition of water as a green solvent. The catalyst was reused several times without loss of its catalytic activity.
Sajjadifar, Sami,Nasri, Parastoo
p. 6677 - 6689
(2017/10/06)

SiO2@FeSO4 nano composite as nanocatalyst for the green synthesis 1,1-diacetates from aldehydes under solvent-free conditions
Aldehydes compounds selective converted to 1,1-diacetates as protective reagent with SiO2@FeSO4 nano composite as effective nano catalyst at room temperature under solvent-free condition and acetic anhydride (Ac2O) as acet
KarimKoshteh, Mostafa,Bagheri, Marziyeh,Zeynizadeh, Behzad
p. 2780 - 2783
(2016/07/12)

Microwave-assisted green synthesis of 1,1-diacetates (acylals) using selectfluor as an environmental-friendly catalyst under solvent-free conditions
An efficient and simple procedure has been developed for the acetylation of aldehyde by selectfluor [1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2,2,2]octane bis(tetrafluoroborate)] as a chemoselective and environmentally friendly catalyst under solvent-free conditions or microwave irradiation. The application of microwave irradiation improved the yields and reduced the reaction times. In this study, selective conversion of aldehydes was observed in the presence of ketones, and the deprotection of 1,1-diacetates has also been achieved using selectfluor in water as green solvent in reflux conditions. The methodology provides synergy of microwave irradiation which offers several advantages such the simple work-up procedure, short reaction time, excellent yields and environmentally benign procedure.
Rezayati, Sobhan,Hajinasiri, Rahimeh,Erfani, Zahra
p. 2567 - 2576
(2016/03/16)

Tungstosulfonic acid as an efficient solid acid catalyst for acylal synthesis for the protection of the aldehydic carbonyl group
Tungstosulfonic acid (TSA) has been found to be an efficient solid acid catalyst for the protection of aldehydic carbonyl groups by geminal diacetate (acylal) formation following the nucleophilic addition of acetic anhydride under neat conditions as well as in a solvent. The TSA catalyst is fully characterized by infrared spectroscopy, wide-angle X-ray scattering analysis, and scanning electron microscopy with energy dispersive X-ray spectroscopy. The deprotection of acylals to corresponding aldehydes has also been investigated under the similar conditions. The catalyst can be reused seven times without a significant loss of activity. In addition, no chromatographic separations are needed to obtain the desired products. This method is a green approach for the chemoselective protection of aldehydes in the presence of ketones.
Kalla, Reddi Mohan Naidu,Kim, Mi Ri,Kim, Yu Na,Kim, Il
supporting information
p. 687 - 693
(2016/01/12)

Formation of benzylidenes-diacetates catalyzed by activated zeolite "LZY-562" and clay (K10/ZnCl2): An unexpected functional selectivity
Activated zeolites LZY-562 and clay montmorillonite K10 at room temperature without solvent catalyzes the synthesis of benzylidenesdiacetates from carbonyl compounds. A chemoselectivity was observed between aldehydes and ketones, between the different aldehydes and ketones as well.
Dokari,Hammadi,Benferrah,Rachedi
p. 1973 - 1976
(2015/12/01)

Zinc zirconium phosphate as an efficient catalyst for chemoselective synthesis of 1,1-diacetates under solvent-free conditions
In the present study, a mild, rapid, and efficient method for the protection of aldehydes with acetic anhydride (AA) in the presence of zinc zirconium phosphate (ZPZn) as a nano catalyst, at room temperature is reported. Selective conversion of aldehydes was observed in the presence of ketones. Under these conditions, different aldehydes bearing electron-withdrawing and electron-donating substituents were reacted with AA and the corresponding 1,1-diacetates (acylals) were obtained in high to excellent yields. The steric and electronic properties of the different substrates had a significant influence on the reaction conditions. Also, the deprotection of 1,1-diacetates has been achieved using this catalyst in water. This nanocatalyst was characterized by several physico-chemical techniques. It was recovered easily from the reaction mixture, regenerated and reused at least 7 times without significant loss in catalytic activity. This protocol has the advantages of easy availability, stability, reusability of the eco-friendliness, chemoselectivity, simple experimental and work-up procedure, solvent-free conditions and usage of only a stoichiometric amount of AA.
Hajipour, Abdol R,Karimi, Hirbod
p. 1945 - 1955
(2015/12/30)

Synthesis of 1,1-diacetates catalyzed by cellulose sulfonic acid from aldehydes and acetic anhydride
1,1-Diacetates have been synthesized in good to excellent yields via a reaction of corresponding aldehydes and acetic anhydride in the presence of cellulose sulfonic acid as a heterogeneous catalyst at room temperature. The protection of aldehydes generated an anhydrodimer as single product under similar reaction conditions. The catalysis is equally applicable for the deprotection of acylal in acetonitrile.
Ding, Songsong,Zhang, Jiming,Shi, Wei,Zhou, Jianhua
p. 340 - 342
(2015/02/19)

Preparation of 1,1-diacetates from aldehydes by LiBH4 and Ac2O in the presence of cation exchange resin
A variety of 1,1-diacetates have been produced from the corresponding aldehydes (1 mmol) by LiBH4(1.25 mmol) and Ac2O (1 mL) in the presence of DOWEX(R)50WX4 (0.5 g) as a cation exchange resinwithin 10 min at room temperature with excellent yields of the products (93-97%).
Rezaeekhordehforosh, Reza,Khezri, Behrooz,Setamdideh, Davood
p. 1205 - 1209
(2015/10/28)

Indium(III)-catalyzed knoevenagel condensation of aldehydes and activated methylenes using acetic anhydride as a promoter
The combination of a catalytic amount of InCl3 and acetic anhydride remarkably promotes the Knoevenagel condensation of a variety of aldehydes and activated methylene compounds. This catalytic system accommodates aromatic aldehydes containing a variety of electron-donating and -withdrawing groups, heteroaromatic aldehydes, conjugate aldehydes, and aliphatic aldehydes. Central to successfully driving the condensation series is the formation of a geminal diacetate intermediate, which was generated in situ from an aldehyde and an acid anhydride with the assistance of an indium catalyst.
Ogiwara, Yohei,Takahashi, Keita,Kitazawa, Takefumi,Sakai, Norio
p. 3101 - 3110
(2015/03/30)

NaBH4/Ac2O/DOWEX(R)50WX4: A convenient system for fast preparation of gem-diacetates from aldehydes
Reductive-acylalation of aldehydes has been carried out by NaBH 4/Ac2O/DOWEX(R)50WX4 system. A variety of aldehydes (1 mmol) have been reacted with Ac2O (0.5 mL) and NaBH4 (1 mmol) in the presence of DOWEX(R)50WX4 (0.5 g) for the preparation of their corresponding acylals within 1 min at room temperature with excellent yields of the products (90-95%). Ketones do not react with this system.
Asl, Parisa Azizi,Setamdideh, Davood
p. 940 - 944
(2014/10/16)

Poly(4-vinylpyridinium) perchlorate as an efficient solid acid catalyst for the chemoselective preparation of 1,1-diacetates from aldehydes under solvent-free conditions
Poly(4-vinylpyridinium) perchlorate has been used as a supported, recyclable, environmentally-benign catalyst for the formation of acylals from aliphatic and aromatic aldehydes in good to excellent yields under solvent-free conditions. Notably, the reaction conditions were tolerant of ketones. This methodology offers several distinct advantages, including its operational simplicity and high product yield, as well as being green in terms of avoiding the use of toxic catalysts and solvents. Furthermore, the catalyst can be recovered and reused several times without any loss in its activity.
Khaligh, Nader Ghaffari
p. 329 - 334
(2014/04/03)

Phospho sulfonic acid as an efficient and recyclable solid acid catalyst for the solvent-free preparation of acylals
Phospho sulfonic acid (PSA) acts as a highly effective and reusable catalyst for the chemo-selective protection of aldehydes with acetic anhydride under solvent-free conditions. The desirable features of this new catalytic methodology include its sustaina
Kalla, Reddi Mohan Naidu,Park, Huiju,Hoang, Trinh Thi Kim,Kim, Il
supporting information
p. 5373 - 5376
(2015/01/09)

Synthesis of 1,1-diacetates catalysed by silica-supported boron sulfonic acid under solvent-free conditions and ambient temperature
1,1-Diacetates derivatives were prepared using the direct condensation of aldehydes with acetic anhydride in the presence of silica-supported boron sulfonic acid (SiO2/B(SO4H)3) as a tri-functional inorganic Bronsted acid catalyst under solvent-free conditions at ambient temperature. The salient features of this methodology are: (i) cheaper process ready availability of the catalyst; (ii) versatility; (iii) high regio-selectivity of the procedure and recyclable property of the catalyst.
Sajjadifar, Sami,Rezayati, Sobhan
p. 531 - 539
(2014/01/17)

P4VP-H2SO4-catalyzed chemoselective protection of aldehydes to acylal along with deprotection reactions
Poly(4-vinylpyridine)-supported sulfuric acid is an excellent reusable heterogeneous catalyst for the chemoselective synthesis of 1,1- diacetates(acylal) from aldehydes in dichloromethane at room temperature within a few minutes. The protection of salicyaldehyde generated an anhydro-dimer as single product under similar reaction conditions. The catalyst is equally applicable for the deprotection of acylal in acetonitrile. The catalyst was prepared by the wet impregnation technique.
Dutta, Papia,Sarma, Parishmita,Borah, Ruli
p. 1378 - 1386
(2013/05/09)

Chemoselective synthesis of geminal diacetates (acylals) using eco-friendly reusable propylsulfonic acid based nanosilica (SBA-15-Ph-PrSO3H) under solvent-free conditions
An expeditious method for the acetylation of aldehydes by mesoporous solid sulfonic acid (SBA-15-Ph-PrSO3H) under solvent-free reaction conditions was described. The route furnished selectively and in excellent yields the corresponding 1,1-diacetates starting from aldehydes and acetic anhydride using the environmentally friendly catalyst. The catalyst was found to be highly active and selective and could be recycled several times.
Zareyee, Daryoush,Moosavi, Sayed M.,Alaminezhad, Alireza
p. 227 - 231
(2013/08/23)

Ultrasound assisted the chemoselective 1,1-diacetate protection and deprotection of aldehydes catalyzed by poly(4-vinylpyridinium)hydrogen sulfate salt as a eco-benign, efficient and reusable solid acid catalyst
Poly(4-vinylpyridinium) hydrogen sulfate solid acid was found to be efficient catalyst for preparation of 1,1-diacetate using ultrasound irradiation at ambient temperature and neat condition. Deprotection of the resulting 1,1-diacetates were achieved using the same catalyst in methanol solvent under ultrasound irradiation at room temperature. This new method consistently has the advantage of excellent yields and short reaction times. Utilization of solvent free, simple reaction conditions, isolation, and purification makes this manipulation very interesting from an economic and environmental perspective. Further, the catalyst can be reused and recovered for several times.
Khaligh, Nader Ghaffari,Shirini, Farhad
p. 19 - 25
(2013/01/15)

A succinimide-N-sulfonic acid catalyst for acetylation reactions in absence of a solvent
A small amount of succinimide-N-sulfonic acid efficiently catalyzed the acetylation of a variety alcohols, phenols, thiols, amines and aldehydes with acetic anhydride at room temperature under solvent free conditions. This catalyst has the advantages of excellent yields and short reaction times and the reaction can be carried out on a large scale, which makes it potentially useful for industrial applications.
Shirini, Farhad,Khaligh, Nader Ghaffari
p. 695 - 703
(2013/08/25)

Sulfonated rice husk ash (RHA-SO3H): A highly powerful and efficient solid acid catalyst for the chemoselective preparation and deprotection of 1,1-diacetates
Rice husk ash (RHA), as a source of amorphous silica, was treated with chlorosulfonic acid and sulfonated rice husk ash (RHA-SO3H) as a highly powerful solid acid catalyst was obtained and characterized with a variety of techniques including IR, TGA, SEM, XRD, pH analysis, Hammett acidity function and BET method. This solid acid showed excellent catalytic activity for the protection and deprotection of aldehydes with Ac2O at room temperature under solvent free conditions. The procedure gave the products in excellent yields in very short reaction times and good to high yields. Also this catalyst can be reused for several times without loss of its catalytic activity.
Shirini, Farhad,Mamaghani, Manouchehr,Seddighi, Mohadeseh
p. 31 - 37
(2013/06/26)

Polystyrene-supported TiCl4 as a novel, efficient and reusable polymeric Lewis acid catalyst for the chemoselective synthesis and deprotection of 1,1-diacetates under eco-friendly conditions
Copolymer beads of styrene and divinylbenzene (5-7%) were synthesized and combined with titanium tetrachloride in CS2 to form a stable complex. The PS/TiCl4 complex was used as a mild and efficient polymer-supported Lewis acid catalyst for the preparation of 1,1-diacetates from various types of aldehydes under heterogeneous conditions at room temperature. Deprotection of the resulting 1,1-diacetates has also been achieved using the same catalyst in methanol. This new protocol has the advantages of easy availability, stability, reusability of the eco-friendly catalyst, high to excellent yields, chemoselectivity, simple experimental and work-up procedure. Moreover, this polymeric catalyst could be recovered easily and reused several times without significant loss in activity.
Rahmatpour, Ali,Mohammadian, Sara
p. 912 - 919
(2013/10/22)

Ultrasound-assisted synthesis of acylals from aldehydes using Mg(CH 3SO3)2-HOAC
An efficient method for the synthesis of acylals from different aldehydes and acetic anhydride in the presence of magnesium methanesulfonate-acetic acid under ultrasound irradiation at room temperature is achieved. Only 1.5mol% of magnesium methanesulfonate and a small quantity of acetic acid are needed to effect the reaction. Selective conversion of aldehydes is observed in the presence of ketones. The catalyst remains active and exhibits no substantial loss of activity or selectivity in up to three reaction cycles.
Liu, Qing,Ai, Hong-Mei,Feng, Shuai
experimental part
p. 122 - 127
(2011/11/01)

A highly efficient solvent-free acetalization of aldehydes to 1,1-diacetates catalyzed by SiO2-Pr-SO3H
1,1-Diacetates are prepared in excellent yields from aldehydes and acetic anhydride under solvent-free conditions at room temperature in short reaction times using catalytic amount of sulfonic acid functionalized silica (SiO 2-Pr-SO3H) which could be easily handled and removed from the mixture of reaction.
Ziarani, Ghodsi Mohammadi,Badiei, Alireza,Shahjafari, Fatemeh,Pourjafar, Taiiebeh
experimental part
p. 10 - 13
(2012/05/19)

Ultrasound-assisted synthesis of acylals catalyzed by stannum (IV) phosphomolybdate under solvent-free condition
An efficient method for the synthesis of acylals from different aldehydes and acetic anhydride in the presence of Keggin-type stannum (IV) phosphomolybdate under ultrasound irradiation at room temperature was achieved. This method provides a new and efficient protocol in terms of cost effective of catalyst, a wide scope of substrates, and simple work-up procedure.
Ai, Hong Mei,Liu, Qing
experimental part
p. 299 - 301
(2012/07/17)

Schiff base complex of metal ions supported on superparamagnetic Fe 3O4@SiO2 nanoparticles: An efficient, selective and recyclable catalyst for synthesis of 1,1-diacetates from aldehydes under solvent-free conditions
We report a new multistep method for preparing functionalized superparamagnetic Fe3O4@SiO2 possessing high saturation magnetization. During the first step, Fe3O 4@SiO2 nanosphere core-shell is synthesized using nano-Fe3O4 as the core, TEOS as the silica source and PVA as the surfactant. Then, Schiff base complex of metal is synthesized from the reaction between Schiff base and metal acetates [Co(OAc)2, Mn(OAc)2, Ni(OAc)2, Cu(OAc)2, Hg(OAc) 2, Cr(OAc)3 and Cd(OAc)2] on the Fe 3O4@SiO2 surface. The structural and magnetic properties of functionalized magnetic silica are identified by transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) instruments. Moreover, functionalized Fe3O4@SiO2 possessed a superparamagnetic characteristic with saturation magnetization value of about 34 emu/g. NMR, FT-IR, elemental analysis and XRD were also used for the identification of these structures. The catalytic ability of Fe 3O4@SiO2/Schiff base complex of metal ions was found to be an efficient nanocatalyst for the conversion of aldehydes to their corresponding 1,1-diacetates compounds under mild and solvent-free conditions at room temperature. This method gives notable advantages such as excellent chemoselectivity, mild reaction condition, short reaction times and excellent yields. Also, the aforementioned nanocatalyst can be easily recovered by a magnetic field and reused for subsequent reactions for at least 5 times without noticeable deterioration in catalytic activity.
Esmaeilpour, Mohsen,Sardarian, Ali Reza,Javidi, Jaber
p. 359 - 367
(2013/02/21)

ZSM-5-SO3H as a novel, efficient, and reusable catalyst for the chemoselective synthesis and deprotection of 1,1-diacetates under eco-friendly conditions
ZSM-5 has been modified as supported sulfuric acid (ZSM-5-SO3H) and introduced for the first time as a mild, convenient, reusable, and heterogeneous catalyst. Various types of aldehydes were efficiently converted to their 1,1-diacetates using a catalytic amount of ZSM-5- SO3H in excellent yields under solvent-free and heterogeneous conditions at room temperature. The deprotection of 1,1-diacetates has also been achieved using this novel catalyst in ethanol. The procedure is operationally simple, environmentally benign, and only a stoichiometric amount of anhydride is used. Springer-Verlag 2011.
Massah, Ahmad Reza,Kalbasi, Roozbeh Javad,Shafiei, Anahita
experimental part
p. 643 - 652
(2012/07/14)

A rapid, convenient and chemoselective synthesis of acylals from aldehydes catalyzed by reusable nano-ordered MCM-41-SO3H
Acylals were prepared by direct condensation of aldehydes with acetic anhydride using nano-ordered MCM-41-SO3H as a heterogeneous catalyst under solvent-free conditions at room temperature in a very short reaction time and excellent yields. The catalyst is recyclable, non-toxic, neither air nor moisture sensitive, and easy to handle. High chemoselectivity toward aldehydes in the presence of ketones is another advantage of the present method which provides selective protection of aldehydes in their mixtures with ketones.
Tourani, Hesam,Naimi-Jamal, Mohammad Reza,Dekamin, Mohammad Ghorban,Amirnejad, Meysam
p. 1072 - 1076
(2013/02/22)

Rice husk supported FeCl3 nanoparticles as an efficient and reusable catalyst for the chemoselective 1,1-diacetate protection and deprotection of aldehydes
1,1-Diacetates were produced from a variety of aromatic aldehydes using rice husk supported FeCl3 nanoparticles as a catalyst. The procedure generally resulted in good yields (98%) of aromatic aldehydes including those carrying electron donating- or withdrawing-substituents. Deprotection of the resulting 1,1-diacetates was also achieved using the same catalyst in ethanol. This new method consistently has the advantages of excellent yields and relatively short reaction times. Further, the catalyst can be reused and recovered for several times.
Shirini, Farhad,Akbari-Dadamahaleh, Somayeh,Mohammad-Khah, Ali
p. 10 - 17
(2012/10/29)

Chemoselective protection and deprotection of aldehydes using solid supported reagent (Silica Chloride) under solvent-free conditions
Silica chloride, a heterogeneous catalyst, has been found to be an efficient catalyst for the protection of aldehydes as acylals under solvent-free conditions, and deprotection of acylals to aldehydes in methanol as a solvent occurred. The reaction takes a shorter time and ensures good to excellent yield of the products.
Datta, Bandita,Pasha
experimental part
p. 1160 - 1166
(2011/05/06)

Chromic(III) sulfamate as a versatile catalyst for organic synthesis
Chromic sulfamate was synthesized and used as catalyst for the first time in various organic reactions such as the transformation of aldehydes or ketones and indole to bis(indolyl)methanes, the transformation of aldehydes and acetic anhydride to 1,1-diacetates and Biginelli reaction. The advantages of the chromic sulfamate are ease of preparation, easy handling, simple work-up and versatility.
Liu, Qing,Li, Zhen
experimental part
p. 3208 - 3210
(2012/02/03)

A convenient and efficient protocol for the synthesis of acylals catalyzed by Br?nsted acidic ionic liquids under ultrasonic irradiation
The synthesis of acylals (1,1-diacetates) via the reactions of aldehydes with acetic anhydride was carried out in 85-97% yields at room temperature under ultrasound irradiation catalyzed by the Br?nsted acidic ionic liquid [bmpy]HSO4. This method provides several advantages, such as solvent-free conditions, operational simplicity, higher yields, and reduced environmental consequences. The ionic liquid was recovered and reused.
Borikar, Sanjay P.,Daniel, Thomas
experimental part
p. 928 - 931
(2012/03/08)

[HSO3-pmim][CH3SO3] as an efficient catalyst for chemoselective synthesis of 1,1-diacetates under ultrasound irradiation
A mild and efficient method for the chemoselective preparation of 1,1-diacetates catalyzed by 1-methyl-3-(3- sulfopropyl)-imidazolium methyl sulfate under ultrasound irradiation has been developed. The yields are ranged in 90%-98%. This protocol offered several advantages including low catalyst loading, high yields, short reaction time and environmentally benign approach.
Li, Chao,Guo, Tao,Zhou, Xin,Wang, Chun,Ma, Jing-Jun,Li, Jin-Bin
experimental part
p. 484 - 487
(2012/04/11)

Synthesis and characterization of BEA-SO3H as an efficient and chemoselective acid catalyst
BEA zeolite was synthesized under hydrothermal condition and modified with various amounts of chlorosulphonic acid. It was characterized by XRD, XRF, FT-IR, BET, thermogravimetric analysis and SEM techniques. Catalytic activity of BEA-SO3H was tested for the synthesis of 1,1-diacetates from a variety of aromatic and aliphatic aldehydes including those carrying electron donating or withdrawing substituents by acetic anhydride. At optimized conditions, The BEA-SO3H (28 wt.%) catalyst showed good yield at very short time for the synthesis and deprotection of 1,1-diacetates. Furthermore, BEA-SO3H was found to be recyclable for the protection of aldehydes with acetic anhydride under solvent-free and room temperature conditions. This method is a green approach for the protection of aldehydes in the presence of ketones.
Kalbasi, Roozbeh Javad,Massah, Ahmad Reza,Shafiei, Anahita
experimental part
p. 51 - 59
(2011/04/15)

Amorphous carbon-silica composites bearing sulfonic acid as solid acid catalysts for the chemoselective protection of aldehydes as 1,1-diacetates and for N-, O- and S-acylations
Amorphous carbon-silica composites bearing sulfonic acid derived from inexpensive natural organic compounds (glucose, maltose, cellulose, chitosan and starch) were prepared by partial carbonization followed by sulfonation and their catalytic activity was evaluated for the protection of aldehydes as 1,1-diacetates and for N-, O- and S-acylations under solvent-free conditions. Different biomaterials have been chosen, with a view to select the most active solid acid catalyst. Carbon-silica composites were characterized by FTIR, XRD and elemental analysis. Sulfonated carbon-silica composite derived from starch was found to be the most active and could be recycled for several runs without loss of significant activity. It was also characterized by TGA, SEM and TEM.
Gupta, Princy,Paul, Satya
experimental part
p. 2365 - 2372
(2011/10/31)

Preparation of silica-bonded propyl-diethylene-triamine-N-sulfamic acid as a recyclable catalyst for chemoselective synthesis of 1,1-diacetates
A simple and efficient procedure for the preparation of silica-bonded propyl-diethylene-triamine-N-sulfamic acid (SPDTSA) by reaction of 3-diethylenetriamine-propylsilica (DTPS) and chlorosulfonic acid in chloroform is described. Silica-bonded propyl-diethylene-triamine-N-sulfamic acid is employed as a recyclable catalyst for the synthesis of 1,1-diacetates from aromatic aldehydes and acetic anhydride under mild and solvent-free conditions at room temperature. Catalyst could be recycled for several times without any additional treatment.
Nouri Sefat, Maryam,Deris, Abdolah,Niknam, Khodabakhsh
experimental part
p. 2361 - 2367
(2012/02/03)

Polystyrene-supported, Al(OTf)3-catalyzed chemoselective synthesis of acylals from aldehydes
Cross-linked polystyrene-supported aluminium triflate [Ps-Al(OTf)3] has been shown to be a mild, efficient, and chemoselective heterogeneous Lewis acid catalyst for acetylation of aldehydes with acetic anhydride. The catalyst can be recovered simply and reused efficiently at least five times without any noticeable loss of catalytic activity. Copyright Taylor & Francis Group, LLC.
Boroujeni, Kaveh Parvanak
experimental part
p. 277 - 284
(2011/03/20)

An efficient method for the transthioacetalization of acylals and acetals under mild conditions
A rapid and efficient method for the transthioacetalization of acylals (1,1-diacetates) and acyclic and cyclic acetals is described. The reaction was carried out using 1-benzyl-4-aza-1-azoniabicyclo[2.2.2]octane tribromide (1 mol%). The yield of the transthioacetalization was high and reaction conditions involve the use of acetonitrile as the solvent at room temperature; isolation is simple and the products are nearly pure.
Pourmousavi, Seied Ali,Hadavankhani, Majid,Zinati, Zahra
experimental part
p. S495-S501
(2012/05/31)

Kinetics and mechanism of the catalytic reaction of ozone with toluene in the liquid phase
The kinetics and product composition of the liquid-phase catalytic oxidation of toluene with an ozone-air mixture were studied. It was shown that at low temperatures in an acetic anhydride medium in the presence of manganese acetate and an inorganic acid, oxidation develops mainly at the methyl group, yielding benzyl acetate, benzaldehyde, and benzylidene diacetate. The scheme of redox catalysis to explain the experimental data is discussed.
Galstyan,Tyupalo,Galstyan
supporting information; experimental part
p. 212 - 215
(2012/04/23)

An efficient and chemoselective procedure for acylal synthesis
A novel heterogeneous efficient procedure has been developed for the chemoselective synthesis of acylals (1,1-diacetates) under solvent-free conditions. A novel catalyst prepared by the sulfuric acid catalyzed copolymerization of p-toluenesulfonic acid and paraformaldehyde displays extremely high activities for the title reactions, affording average yields over 90% within several minutes. A comparative study showed that the novel catalyst has much higher activity than other catalysts used for this purpose. Besides, the novel catalyst displays chemoselectivity for the protection of aldehydes in the presence of ketones. In addition the high acidity (4.0 mmol/g), thermal stability (200 °C) and easy reusability make the novel catalyst one of the best choices for the process.
Fan, Da-He,Wang, Hui,Mao, Xing-Xing,Shen, Yong-Miao
experimental part
p. 6493 - 6501
(2010/11/04)

Conjugate addition of indole to α,β-unsaturated ketones catalyzed bylewis acid immobilized on a biorenewable support
Sulfonated carbonaceous solid acid was prepared straightforwardly from household granulated sucrose through a one-pot carbonization-sulfonation process. The performance of this solid Bronsted acid was tested by the 1,1-diacylation of aldehydes. Lewis acid, such as indium chloride, was supported on sucrose- derived carbonaceous solid acid through anion metathesis and successfully applied to the conjugate addition of indole to α,β- unsaturated ketones.
Li, Bei-Yao,Zhang, Miao,Yan, Xin-Min,Peng, Yan-Qing
experimental part
p. 1243 - 1247
(2011/10/07)

Mild and chemoselective synthesis and deprotection of geminal diacetates catalyzed by titanium(IV) halides
A novel, mild, and chemoselective method was developed for the preparation of gem-diacetates from aldehydes and acetic anhydride in the presence of titanium(IV) fluoride (1-5 mol%) under solvent-free conditions at room temperature. The reaction showed a high chemoselectivity toward aldehydes in the presence of ketones. Moreover, titanium(IV) fluoride also catalyzed the deprotection of gem-diacetates to the corresponding aldehydes in water. This efficient and simple method has several benefits, including the use of an inexpensive catalyst, solvent-free conditions, mild reaction temperatures, and high yields, which make it both cost-effective and environmentally friendly. Georg Thieme Verlag Stuttgart.
Jung, Misuk,Yoon, Jieun,Kim, Hak Sung,Ryu, Jae-Sang
experimental part
p. 2713 - 2720
(2010/10/02)

Visible light flavin photo-oxidation of methylbenzenes, styrenes and phenylacetic acids
We report the photocatalytic oxidation of benzylic carbon atoms under mild conditions using riboflavin tetraacetate as photocatalyst and blue-emitting LEDs (440 nm) as light source. Oxygen is the terminal oxidant and hydrogen peroxide appears as the only byproduct in most cases. The process oxidizes toluene derivatives, stilbenes, styrenes and phenylacetic acids to their corresponding benzaldehydes. A benzyl methyl ether and acylated benzyl amines are oxidized directly to the corresponding methyl ester or benzylimides. The mechanism of the reactions has been investigated and the results indicate that oxygen addition to benzyl radicals is a key step of the oxidation process in the case of phenylacetic acids.
Lechner, Robert,Kuemmel, Susanne,Koenig, Burkhard
experimental part
p. 1367 - 1377
(2011/12/01)

Chemoselective synthesis of 1,1-diacetates from aldehydes using anhydrous cobalt(II) bromide under solvent-free conditions
A mild and efficient method has been developed for the chemoselective preparation of 1,1-diacetates (acylals) from aldehydes catalyzed in the presence of a catalytic amount (0.1mmol) of anhydrous cobalt(II) bromide under solvent-free conditions. The remarkable selectivity under mild and neutral conditions, excellent yields, short reaction time, and easily available and inexpensive catalyst are important features of this method.
Meshram, Gangadhar A.,Patil, Vishvanath D.
experimental part
p. 442 - 449
(2010/04/02)

Silica phosphoric acid: An efficient and recyclable catalyst for the solvent-free synthesis of acylals and their deprotection in MeOH
Silica phosphoric acid was used as an efficient, mild, and recyclable solid catalyst for the synthesis of acylals from various structurally diverse aldehydes and acetic anhydride under solvent-free conditions. The acylation of aldehydes was highly chemoselective, and no ketone was acylated, which provided a method for the synthesis of acylals from aldehydes in the presence of ketones. Silica phosphoric acid-catalyzed deprotection of acylals to the corresponding aldehydes in MeOH has also been developed with excellent yield. The deprotection of the acylals of aromatic aldehydes took priority over those of aliphatic aldehydes. Copyright Taylor & Francis Group, LLC.
Zhang, Fuyi,Liu, Hong,Zhang, Qing-Ju,Zhao, Yu-Fen,Yang, Feng-Ling
scheme or table
p. 3240 - 3250
(2010/12/24)

Sulphated zirconia as an eco-friendly catalyst in acylal preparation under solvent-free conditions, acylal deprotection assisted by microwaves, and the synthesis of anhydro-dimers of o-hydroxybenzaldehydes
A solvent-free approach is described for the regioselective synthesis of acylals (1,1-diacetates) in shorter reaction times and higher yields, compared to conventional methodology using solvents. In the protection reaction of the o-hydroxybenzaldehyde the formation of acetyl compounds and anhydro-dimers was observed. The deprotection reaction involves microwave (MW) exposure of diluted reactants in the presence of solid sulphated zirconia (SZ) catalyst that can be easily recovered and reused. The sulphated zirconia was recycled several times without any loss of activity.
Palacios-Grijalva, Laura Nadxieli,Cruz-Gonzalez, Deysi Y.,Lomas-Romero, Leticia,Gonzalez-Zamora, Eduardo,Ulibarri, Gerardo,Negron-Silva, Guillermo E.
experimental part
p. 4065 - 4078
(2010/03/01)

NbCl5 as an efficient catalyst for chemoselective synthesis of 1,1-diacetates under solvent-free conditions
A mild and efficient method for the chemoselective preparation of 1,1-diacetates catalyzed by NbCl5(5mmol%) under solvent-free conditions has been developed. The yields are in the range of 93-98%. This protocol offered several advantages, including low catalyst loading, good yields, short reaction times, and environmentally friendliness.
Gao, Shu-Tao,Zhao, Ying,Li, Chao,Ma, Jing-Jun,Wang, Chun
experimental part
p. 2221 - 2229
(2009/10/17)