Rapid deprotection of <Emphasis Type="BoldItalic">N</Emphasis>-Boc amines by TFA combined with freebase generation using basic ion-exchange resins

Summary The deprotection of N-Boc amines was rapidly accomplished using 5 equivalents of TFA in methylene chloride in a focused microwave instrument with irradiation at 60 ^∘C for 30 min. The freebase amines are then obtained by scavenging the crude reaction mixture with the basic Amberlyst A-21 ion-exchange resin. This procedure is suitable for the parallel deprotection of N-Boc amines.     

Nickel boride mediated chemoselective deprotection of 1,1-diacetates to aldehydes and deprotection with concomitant reduction to alcohols at ambient temperature

A variety of 1,1-diacetates have been chemoselectively and efficiently deprotected to the corresponding aldehydes as well as deprotected and concomitantly reduced to the corresponding alcohols in high yields at ambient temperature with nickel boride generated in situ using different molar ratios of sodium borohydride and nickel (II) chloride in methanol at room temperature. Deprotection and reduction of a variety of aromatic, aliphatic and heterocyclic acylals have been achieved efficiently. Mild reaction conditions, easy work-up, high yields and chemoselectivity demonstrate the efficiency of this new method.     

Samarium(II) dibromide-promoted selective deprotection of a benzoyl protective group

The selective deprotection of a benzoyl group was very important methodology in the field of organic synthesis. Various methods for debenzoylation were investigated and developed in the past six decades, but more useful and selective strategies are now being strongly desired. In response to this strong demand, we developed the novel and selective deprotection of a benzoyl group by use of samarium(II) dibromide and a proton source. This deprotective reaction proceeded smoothly and the desired compound was obtained in good to excellent yields. In this paper, we will report the details of this deprotective reaction.     

Unexpected tosyl deprotection during osmium catalysed dihydroxylation

Depending on the double bond position, tosyl deprotection was observed during olefin dihydroxylation using osmium tetroxide, leading to triols.     

Selective Protection of Carbonyl Compounds as Azines and Their Facile Regeneration

Carbonyl compounds with freshly prepared hydrazinium formate successfully yielded the corresponding azines in excellent yields. In turn, azines were deprotected to the corresponding carbonyls using triethylammonium chlorochromate chemoselectively.     

Microwave-assisted N-debenzylation of amides with triflic acid

A new and facile microwave-assisted protocol for the debenzylation of N-benzylamides with triflic acid has been developed. Both secondary and tertiary aliphatic or aromatic amides are obtained in moderate to good yields.     

Selective Deprotection of Fully Benzoylated Nucleoside Derivatives

Abstract

Selective deprotection of benzoylated hydroxyl groups is one of the crucial problems in the synthesis of nucleoside analogues as well as of other polyfunctional molecules.     

Protection and deprotection chemistry catalyzed by zirconium oxychloride octahydrate (ZrOCl2·8H2O)

Abstract

An efficient, chemoselective, convenient, and straightforward methodology has been developed for the protection of C=O group of aldehydes/ketones as C=N moiety of hydrazones catalyzed by ZrOCl₂·8H₂O (10 mol%) in acetonitrile and the same catalyst in methanol oxidatively cleaves C=N moiety of hydrazones to provide parent carbonyl compounds in high yields. The reactions have been performed in aerobic condition. The catalyst is inexpensive, readily available, easy to handle, insensitive to air and moisture, easily recoverable and can be reused and importantly less toxic.     

Positional chemoselectivity in the Zn(II)-mediated removal of phenol protecting groups

A protocol was developed for the chemoselective ortho-deprotection of polyphenolic substrates using readily available Zn^IIX₂ salts. This procedure provides exceptional positional selectivity for the deprotection of phenols that reside adjacent to directing carbonyl functionality in the presence of similar protecting groups at the meta and para positions. Good to excellent yields of the desired free phenols were obtained (?96%), and a wide assortment of protecting groups was readily removed under the reaction conditions.     

A Simple Homemade Reaction Station for use in Parallel Solution-Phase Synthesis. Optimization of a Regioselective One-Step Deprotective o-formylation Reaction Mediated by the Vilsmeier-Haack Reagent POCl3⋅DMF

Summary We report herein the fabrication of a simple and price-affordable portable reaction station for use in parallel solution-phase synthesis. This homemade device uses currently available laboratory components and equipment. Specifically designed to fit standard magnetic hotplates/stirrers, it can simultaneously hold up to 24 heated and magnetically stirred glass reactors of both 10 and 50 mL capacities. Glass reactors are connected by flexible 16-gauge metal needles to a central gas manifold equipped with an inlet/outlet for vacuum and inert gases. Reaction temperatures can be optimally varied from −78 ^∘C to 150 ^∘C. Using a statistical screening DOE method, this parallel array reactor station has been successfully operated to optimize the one-step deprotective O-formylation of a sterically hindered bis-O-tert-butyldiphenylsilyl (O-TBDPS) aromatic diol. The latter transformation was mediated by the Vilsmeier-Haack reagent POCl₃⋅DMF using a range of Lewis acid and metal salt promoters, including their binary combinations.