- Stable Benzylic (1-Ethynylcyclohexanyl)carbonates Protect Hydroxyl Moieties by the Synergistic Action of [Au]/[Ag] Catalytic System
-
Chemical syntheses of oligosaccharides and glycosides call utilization of many protecting groups that can be installed or deprotected without affecting other functional groups present. Benzyl ethers are routinely used in the synthesis of glycans as they can be subjected to hydrogenolysis under neutral conditions. However, installation of benzyl ethers is often carried out under strong basic conditions using benzyl halides. Many a times, strongly basic conditions will be detrimental for some of the other sensitive functionalities (e.g., esters). Later introduced reagents such as benzyl trichloroacetimidate and BnOTf are not shelf-stable, and hence, a new method is highly desirable. Taking a cue from the [Au]/[Ag]-catalyzed glycosidations, we have identified a method that enables protection of hydroxyl groups as benzyl, p-methoxybenzyl, or naphthylenemethyl ethers using easily accessible and stable carbonate reagent. A number of saccharide-derived alcohols were subjected to the benzylation successfully using a catalytic amount of gold phosphite and silver triflate. Furthermore, the protocol is suitable for even protecting menthol, cholesterol, serine, disaccharide OH, and furanosyl-derived alcohol easily. The often-utilized olefins and benzoates, as well as benzylidene-, silyl-, Troc-, and Fmoc-protecting groups do not get affected during the newly identified protocol. Regioselective protection and one-pot installation of benzyl and p-methoxybenzyl ethers are demonstrated.
- Chakraborty, Saptashwa,Mishra, Bijoyananda,Neralkar, Mahesh,Hotha, Srinivas
-
p. 6604 - 6611
(2019/06/14)
-
- Selective catalytic synthesis of unsymmetrical ethers from the dehydrative etherification of two different alcohols
-
The cationic ruthenium-hydride complex [(C6H6)(PCy3)(CO)RuH]+BF4- catalyzes selective etherification of two different alcohols to form unsymmetrically substituted ethers. The catalytic method exhibits a broad substrate scope while tolerating a range of heteroatom functional groups in forming unsymmetrical ethers, and it is successfully used to directly synthesize a number of highly functionalized chiral nonracemic ethers.
- Kim, Junghwa,Lee, Dong-Hwan,Kalutharage, Nishantha,Yi, Chae S.
-
p. 3881 - 3885
(2015/01/16)
-
- Simple and efficient method for the protection of hydroxyl groups as 4-methoxybenzyl ethers
-
PMB ethers of alcohols are obtained in good yields and under mild conditions using the 4-methoxybenzyl N-allyl thiocarbamate and N-bromosuccinimide (NBS)/TfOH as the catalyst. The present method is very fast, simple, and efficient. Copyright
- Kasprzycka, Anna,Ptaszek-Budniok, Agata,Szeja, Wies?aw
-
p. 2276 - 2284
(2014/07/07)
-
- A convenient approach for the deprotection and scavenging of the PMB group using POCl3
-
A convenient and high yielding approach for the deprotection and scavenging of the p-methoxybenzyl (PMB) group in PMB ethers and PMB esters was developed using POCl3 as the reagent. 4-Methoxybenzyl chloride, a starting material used for the preparation of PMB ethers and esters was regenerated in the deprotection step. This mild and selective procedure tolerates several acid sensitive functional groups. The Royal Society of Chemistry 2013.
- Ilangovan, Andivelu,Saravanakumar, Shanmugasundar,Malayappasamy, Subramani,Manickam, Govindaswamy
-
p. 14814 - 14828
(2013/09/02)
-
- Silver(I)-Catalyzed deprotection of p -methoxybenzyl ethers: A mild and chemoselective method
-
The p-methoxybenzyl protecting group (PMB) on various alcohols and an acid was efficiently and selectively cleaved by the action of a catalytic amount of silver(I) hexafluoroantimonate combined with 0.5 equiv of 1,3,5- trimethoxybenzene in dichloromethane at 40 °C.
- Kern, Nicolas,Dombray, Thomas,Blanc, Aurelien,Weibel, Jean-Marc,Pale, Patrick
-
p. 9227 - 9235,9
(2012/12/12)
-
- Mild, selective deprotection of PMB ethers with triflic acid/1,3-dimethoxybenzene
-
An efficient method for the cleavage of the p-methoxybenzyl protecting group of several alcohols in the presence of 0.5 equiv of trifluoromethanesulfonic acid and 1,3-dimethoxybenzene in dichloromethane at room temperature is described.
- Jung, Michael E.,Koch, Pierre
-
experimental part
p. 6051 - 6054
(2011/11/28)
-
- An efficient means for generating p-methoxybenzyl (PMB) ethers under mildly acidic conditions
-
The protection of a wide variety of alcohols as their p-methoxybenzyl ethers can be performed with PMBO-lepidine in the presence of methyl tosylate or, preferably, camphorsulfonic acid. No inorganic promoters are required, thereby facilitating workup and product isolation. Georg Thieme Verlag Stuttgart.
- Stewart, Catherine A.,Peng, Xiaowen,Paquette, Leo A.
-
p. 433 - 437
(2008/09/20)
-
- Synthesis of para-methoxybenzyl (PMB) ethers under neutral conditions
-
2-(4-Methoxybenzyloxy)-4-methylquinoline reacts with methyl triflate in the presence of alcohols to generate a neutral organic salt that transfers the para-methoxybenzyl (PMB) protecting group onto alcohols in high yield and under mild conditions. The Royal Society of Chemistry.
- Nwoye, Ernest O.,Dudley, Gregory B.
-
p. 1436 - 1437
(2008/02/02)
-