Ferf-Butyl carbamate

The deprotection of f-Boc proline ester 2a is representative of the general procedure employed. ferf-Butyl carbamate (0.217 g, 1.0 mmol) and aluminium chloride (0.134 g, 1.0 mmol) doped on a neutral alumina (1.0 g) were mixed thoroughly on a vortex mixer. The reaction mixture was placed in an alumina bath inside an unmodified household microwave oven (operating at frequency 2450 MHz) and irradiated for a period of 1 min. After completion of the reaction (monitored by TLC, EtOAc-hexane, 9 1 v/v), it was neutralized with aqueous sodium bicarbonate solution and the product was extracted into ethyl acetate (2x15 mL). The ethyl acetate layer was separated, dried over magnesium sulfate, fdtered, and the crude product thus obtained was purified by column chromatography to afford pure methyl ester 2b in 88% yield. 

Buchwald et al. reported a Cu(I)-catalyzed domino amidation/hydroamidation procedure of l-halobut-l-en-3-ynes 28 with ferf-butyl carbamate to form substituted W-Boc-protected pyrroles 29 (Scheme 9) [55]. 

With no fear, we pushed on to the Curtius rearrangement sequence needed to transform ferf-butyl ester 44 into the amide needed for sorbicillactone A. In the same fashion as the model substrate, the ester was first converted into acyl azide 45. Heating the acyl azide in a solution of f-BuOH under microwave conditions gave the rearranged product as ferf-butyl carbamate 46. Alternatively, and more directly, the rearrangement of acyl azide 45 to the isocyanate could be performed in THF. Subsequent hydrolysis with aqueous K2CO3 afforded the amine, which was acylated with fumarate 30 to give amide 47. 

Purpose To demonstrate the protection of the amine group of an a-amino acid by forming a ferf-butyl carbamate. 

Fuming 100%-HNO3 added dropwise at 0 to acetic anhydride, then the temp, allowed to rise to 20°, ethyl N-(ferf-butyl)carbamate added at 20-25° with stirring, which is continued 30 min. at 25-30° ethyl N-ferf-butyl-N-nitro-carbamate. Y 70%. F. e. s. 

Keywords Aryl bromides, ferf-butyl carbamate, Pd2(dba)3.CHCl3, ligand 1, BuONa, toluene, room temperature, amidation, N-Boc-protected anilines... 

BOC-L-valinal = ferf-butyl A/-[(1S)-1-(methylethyl)-2-oxoethyl]carbamate Scheme 9... 

Reaction of 9-fluoro-7-oxo-2,3-dihydro7H-pyrido[l,2,3-de][l,4]oxa-zine-6-carboxylate and ferf-butyl (2-mercaptoethyl)carbamate in DMSO at 100 °C for 5 h gave 9-[2-(ferc-butoxycarbonylamino)ethylthio] derivative (06WOP2006/050943). The iodo atom of 9-iodo-7-oxo-2,3-dihydro-7H-pyrido[l,2,3-de][l,4]oxazine-6-carboxylic acids was coupled with 4 -0-(2-allyloxyethyl)azithromicin in MeCONMe2 in the presence of Bu3N and fra s-di-g-acetato-bis[2-(di-o-tolylphosphino)benzyl]dipalladium(II) and di(ferf-butyl)-4-methylphenol at 110-115 °C for 15-17 h to give a mixture of 9-(3-substituted prop-1- and -2-enyl) derivatives (07WOP2007/ 054296). 10-methoxy and 10-cyano-3-hydroxymethyl-2,3-dihydro-5H-pyr-ido[l,2,3-de][l,4]benzoxazin-5-ones were obtained from 10-bromo derivative by reaction with NaOMe in the presence of Cu(I)I at 140 °C in DMF,... 

Irradiation of a ferf-butyl alcohol solution of 2-ethoxy-pyrroline-5-one (12) with Vycor filtered light from a 450-W mercury lamp results in formation of ferf-butyl N-(ethoxycyclopropyl) carbamate (13) in 73% isolated yield17,18 When the irradiation is conducted in the non-hydroxylic solvent, tetrahydrofuran, 1-ethoxycyclo-propyl isocyanate (20) can be isolated in 78% yield. Both 13 and 20 can be prepared in synthetically useful quantities. 

Fig. 4.32. Three El eliminations in the deprotection of a protected tripeptide. For the sake of brevity, a single formula in the second row of the scheme shows how the three ferf-Bu—O bonds heterolyze of course, they are activated and broken one after the other. In the deprotection of the ferf-butylated lysine side chain, the leaving group is a carbamic acid. Carbamic acids decar boxylate spontaneously (Figure 7.12), which explains the final transformation. The preparation of the protected tripeptide is shown in Figure 4.35.

In peptide synthesis functional groups in the amino acid side chains are often protected with acid-labile protecting groups (Section 4.5.3). The tripeptide in Figure 4.35 contains, for example, a serine ferf-butyl ether and an L-lysine e-protected as an O-tert-butyl carbamate. In the standard strategy of synthesizing oligopeptides from the C- to the N-terminus (cf. Section 6.4.3) the C-terminus is either connected to the acid-labile... 

The Boc group is easily cleaved by brief treatment with trifluoroacetic acid (TFA), CF3COOH. Loss of a relatively stable ferf-butyl cation from the protonated ester gives an unstable carbamic acid. Decarboxylation of the carbamic acid gives the deprotected amino group of the amino acid. Loss of a proton from the fert-butyl cation gives isobutylene. 

Many functional groups are stable under conditions for the alkylation of pseudoephedrine glycinamide enolates, including aryl benzenesulfonate esters (eq 18), rert-butyl carbamate and rerf-butyl carbonate groups (eq 19), tert-butyldimethylsilyl ethers, benzyl ethers, ferf-butyl ethers, methoxymethyl ethers, and alkyl chlorides. The stereochemistry of the alkylation reactions of pseudoephedrine glycinamide and pseudoephedrine sarcosinamide is the same as that observed in alkylations of simple A(-acyl derivatives of pseudoephedrine. 

In amino acid and peptide chemistry, the di-ferf-butyl dicarbonate (BocaO) is an extensively used reagent for the clean and rapid Boc-protection of amine functionalities.It is also an efficient ferf-butoxycarbonylating agent for alcohols, thiols, and carbon nucleophiles, and it has been used for the conversion of amines into isocyanates, carbamates, and urea derivatives.The reaction of amino acids with chloroformates to produce N-urethane-protected amino acids if not performed under optimal conditions is accompanied by the formation of N-protected oligomers this has been well documented in the case of and... 

Ethoxypyrrolin-5-one l-Pyrrolin-5-one, 2-ethoxy- (8) 2H-Pyrrol-2-one, 5-ethoxy-3,4-dihydro- (9) (29473-56-1) ferf-Butyl N-(l-ethoxycyclopropyl)carbamate Cyclopropanecar-bamic acid, 1-ethoxy-, fert-butyl ester (8) Carbamic acid, (1-ethoxycyclopropyl)-, 1,1-dimethylethyl ester (9) (28750-48-3 41879-49-6)... 

Some results regarding thermal decomposition of various vinyl polymers from this group are summarized in Table 6.5.10. The polymer list includes poly(ferf-butyl-N-vinyl carbamate), poly(N-vinylcarbazole), two halogenated poly(N-vinylcarbazoles), two poly(vinylpyridines), and poly(vinyltrimethyl-silane). 

Otlier preparative methods for phosphorylglycines include the addition of sodium diethyl pliosplute to the Schiff base prepared from benzylamine and ethyl or ferf-butyl glyoxalate - the reaction of McjSiBr with the triethoxyphosphorane prepared from Af-protected alkyl oxalamides and trietliyl phosphite and the Rh(II)-catalyzed N-H insertion of diethyl 1-ethoxycarbonyl-l-diazomethylphosphonate into carbamates. 

Accordingly, experimental conditions [phosgene mixed with 2,6-di(ferf-butyl)pyridine and addition of triethylamine (5 equiv)] that favor the formation of the carbamoyl chloride 71 rather than isocyanate 69 were chosen. The result is that the post-barrier carbamate 70 was formed from... 

In each step of the usual C-to-N peptide synthesis the N-protecting group of the newly coupled amino acid must be selectively removed under conditions that leave all side-chain protecting groups of the peptide intact. The most common protecting groups of side-chains (p. 229) are all stable towards 50% trifluoroacetic acid in dichloromethane, and this reagent is most commonly used for N -deprotection. Only ferf-butyl esters and carbamates (=Boc) are solvolyzed in this mixture. 

Tosylimino)phenyl-X -iodane, another iodine(III)-based reagent, also facilitates the conversion of a large variety of amides such as 16 into the corresponding isocyanates 17, which are suitable precursors for the synthesis of methyl carbamates 18 as shown in Scheme 6 [6]. The reaction proceeds in very good yields with a variety of electron-rich and electron-poor aryl-substituted amides as well as bulky alkyl-substituted amides. Although no conversion was observed when a 2,4,6-trimethylphenyl substituent was present, the authors successfully synthesized isopropyl Af-(4-methylphenyl)carbamate and ferf-butyl iV-(4-methylphenyl)carbamate by treatment of the corresponding isocyanates with suitable alcohols. 

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