Towards a selective Boc deprotection on acid cleavable Wang resin

Deprotection of the Boc group of an amino acid attached to the Wang resin has been investigated. Several conditions, including bases, solvents and reaction time, were studied. Quantitative yield of Boc deprotection was achieved with less than 10% loss of resin loading with trimethylsilyltriflate. This reagent allows the replacement of tert-butyl to TMS group, leading to a new temporary urethane protection readily hydrolyzed.     

A mild and practical deprotection method for benzyl thioethers

A highly effective and mild deprotection method was developed for benzyl thioethers using dibutylmagnesium in the presence of a catalytic amount of titanocene dichloride. This methodology is applicable to both aromatic and aliphatic benzyl thioethers.     

An exceptionally mild deprotection of phthalimides

Phthalimides are converted to primary amines in an efficient, two-stage, one-flask operation using NaBH₄/2-propanol, then acetic acid.     

A mild copper catalyzed method for the selective deprotection of aryl allyl ethers

Copper boryl reagents enable the selective cleavage of aryl allyl ethers to the corresponding phenols in good to moderate yields.     

A mild and selective method for the N-Boc deprotection by sodium carbonate

A cleavage of N-tert-butyloxycarbonyl protection by Na₂CO₃ is reported. The N-free products are obtained in excellent yields. The compatibility of the method with the presence of acidic or basic groups is demonstrated. The reactions were performed on indole, azaindole, indazole, pyrazole, indolinone, quinolinone, and oxazolone.     

Zinc triflate: A mild and efficient catalyst for deprotection of tetrahydropyranyl ethers

Treatment of tetrahydropyranyl (THP) ethers with zinc triflate in methanol provides a simple and efficient process for deprotection of these ethers and the parent alcohols are obtained in excellent yields.     

A systematic study of two complementary protocols allowing the general,mild and efficient deprotection of N-pivaloylindoles

Two mild and general protocols for the high-yielding deprotection of indoles and related fused heterocyclic systems are described, involving either hydride transfer from LDA or hydrolysis by the DBU–water system. Both methods were shown to tolerate a wide variety of substituents and functional groups, but the hydrolytic one proved to be particularly general, being compatible with 2-alkyl substituents, aldehydes, ketones, carboxylic acids, halogens, ethers, amides and esters. Yields were normally excellent in both cases, but were usually slightly higher for the reductive method. Taken together, these two protocols provide a general solution to the problem of pivaloyindole deprotection.     

A mild, efficient and selective deprotection of t-butyldimethylsilyl-protected phenols using cesium carbonate

A mild and efficient method for the deprotection of aryl t-butyldimethysilyl (TBS) ethers is described. The protecting group TBS could be cleaved from aryl silyl ethers using cesium carbonate in DMF-H₂O at room temperature to give the corresponding phenols in excellent yields. The reaction conditions allowed selective deprotection of aryl TBS-protected phenols in the presence of TBS, phenyloxycarbonyl or tetrahydropyranyl-protected alcohols.     

A mild,copper-catalysed amide deprotection strategy: use of tert-butyl as a protecting group

Mild methods for the deprotection of organic substrates are of fundamental importance in synthetic chemistry. A new room temperature method using a catalytic amount of Cu(OTf)₂ is reported. This allows use of the tert-butyl group as an amide protecting group. The methodology is also extended to Boc-deprotection.     

Aqueous phosphoric acid as a mild reagent for deprotection of the t-butoxycarbonyl group

Aqueous phosphoric acid (85 wt%) is an efficient and mild reagent for the deprotection of N-BOC groups. Acid sensitive functionalities including benzyl and methyl esters, TBDMS ether, CBZ and isopropylidene groups are compatible with the reaction conditions. The reactions are high yielding, and the workup is convenient.     

Solid-supported acids as mild and versatile reagents for the deprotection of aromatic ethers

p-Toluene sulfonic acid (p-TsOH) immobilized either on polystyrene (PS) or silica (Si) was found to be effective in cleaving aromatic ethers containing isopropyl, tert-butyl, allyl, and benzyl groups, as well as mono-, di-, and trimethoxylated benzyl groups, in moderate to excellent yields (54-95%). These protecting groups could be selectively deprotected when they were simultaneously present on the same or different aromatic rings in a substrate.     

Novel deprotection of SEM ethers: A very mild and selective method using magnesium bromide

New lability and stability sequences have been established for multifunctional substrates containing SEM ether group(s) by a MgBr(2)/Et(2)O/MeNO(2) deprotection protocol.     

A mild deprotection strategy for allyl-protecting groups and its implications in sequence specific dendrimer synthesis

A mild deprotection strategy for allyl ethers under basic conditions in the presence of a palladium catalyst is described. Under these conditions, aryl allyl ethers can be cleaved selectively in the presence of alkyl allyl ethers. These conditions are also effective in the deprotection of allyloxycarbonyl groups. The utility of the current methodology in sequence specific dendrimer synthesis is demonstrated.     

A technetium intermediate specifically promotes deprotection of trifluoroacetyl HYNIC during radiolabelling under mild conditions

The trifluoroacetyl group protects the nucleophilic HYNIC from unwanted side reactions yet allows radiolabelling with technetium-99m under mild conditions, due to efficient and specific promotion of deprotection by a technetium complex intermediate.     

A mild and efficient method for the chemoselective deprotection of acetonides with lanthanum(III) nitrate hexahydrate

Acetonides are hydrolyzed selectively and efficiently with lanthanum(III) nitrate hexahydrate in acetonitrile. The method has good compatibility with other sensitive hydroxyl protecting groups such as trityl, TBDMS, THP, OAc, OBz and OBn.     

A mild and efficient method for the selective deprotection of silyl ethers using KF in the presence of tetraethylene glycol

A mild and efficient protocol for the deprotection of silyl ethers using KF in tetraethylene glycol is reported. A wide range of alcoholic silyl ethers can be selectively cleaved in high yield in the presence of certain acid- and base-labile functional groups. Moreover, the phenolic silyl ethers were cleaved exclusively, without affecting the alcoholic silyl ethers, at room temperature.     

Aqueous phosphoric acid as a mild reagent for deprotection of tert-butyl carbamates, esters, and ethers

Aqueous phosphoric acid (85 wt %) is an effective, environmentally benign reagent for the deprotection of tert-butyl carbamates, tert-butyl esters, and tert-butyl ethers. The reaction conditions are mild and offer good selectivity in the presence of other acid-sensitive groups, including CBZ carbamates, azetidine, benzyl and methyl esters, TBDMS, and methyl phenyl ethers. The mildness of the reaction is further demonstrated in the synthesis of clarithromycin derivative, in which a tert-butyl ester is removed in the presence of cyclic carbamate, lactone, ketal, acetate ester, and epimerizable methyl ketone functionalities. The reaction preserves the stereochemical integrity of the substrates. The reactions are high yielding, and the workup is convenient.     

Boron trifluoride-methanol complex—mild and powerful reagent for deprotection of labile acetylated amines

A set of amino-group possessing cyanine dyes is obtained from their N-acetyl derivatives via deprotection with boron trifluoride-methanol complex in good yields.     

A mild and efficient approach for the selective deprotection of benzyl and phenyl trimethylsilyl ethers in 1-butyl-3-methyl-imidazolium chloride

1-Butyl-3-methyl-imidazolium chloride ([bmim]Cl) in the absence of any catalyst mediated the selective deprotection of benzyl and phenyl trimethylsilyl (TMS) ethers to the corresponding alcohols and phenol in good yields at room temperature even in presence of alkyl silyl ethers. The work-up of reactions is very simple and the products do not require further purification. The ionic liquid (IL) can be recycled and reused for several runs without any significant loss of activity.