Benzyl Chloroformate used in the amine protection
Cbz is another popular carbamate used in the amine protection. It could be easily deprotected under hydrogenation or triethyl silane.Gabriel Amine synthesis is similar to this protection, go figure out the rest of the mechanism.Dimethyl Pyrrole protection is very useful in primary amine protection, especially you could not have active proton in your molecule.
Fmoc has very good stability in acidic condition, and reasonable stability in inorganic base. It could be removed in a couple minutes with piperidine. You can see a very bright blue spot on your TLC solvent front line. Boc is used extensively in amine protection. It is stable under base condition, could be easily get rid of under TFA/CH2Cl2 (1/1). Boc could be reduced to methyl group under LAH to make single methyl substitution.
Benzyl chloroformate(CAS NO: 501-53-1) is the benzyl ester of chloroformic acid. It is also known as benzyl chlorocarbonate and is an oily liquid whose color is anywhere from yellow to colorless. It is also known for its pungent odor. When heated, benzyl chloroformate decomposes into phosgene and if it comes in contact with water it produces toxic, corrosive fumes.
Benzyl chloroformate(CAS NO:501-53-1) is used in organic synthesis for the introduction of the carboxybenzyl (Cbz or Z) protecting group for amines:
Benzyl protection of phenol. The starting material, phenol (1 equiv.), was dissolved into acetone. BnBr (1.3 equiv.), and K2CO3 (15 equiv.) were added into the acetone solution. The resulting mixture was refluxed for 2 hours. After filtered the solid, the filtrate was concentrated, and the residue was separated by a silica gel plug.
Deprotection of benzyl group: The starting material was dissolved into ethanol with Pd on C. The mixture was put on parr shaker with H2 30 psi for 3 hours. The resulting mixture was filtered, and the filtrate was concentrated to afford almost pure product.
Boc protection of amine group: Amine (1equiv.) and Boc2O (1.5 equiv.) were dissolved into methylene chloride with TEA(2 equiv.). The mixture was stirred for 6 hours at room temperature. The resulting mixture was washed with brine, and the organic layer was dried and concentrated. The resulting residue was separated by silica gel column.
Benzyl chlorofomate amine protection: Amine ( 1equiv.) and TEA (2 equiv.) were dissloved into THF. To the solution, benzyl chloroformate was added dropwise. The resulting mixture was stirred for 4 hours. The precipitate was filtered. Ethyl acetate was added into the organic solution. Brine was used to wash the organic layer. The organic layer was dried, concentrated. The resulting residue was separated by silica gel column to afford 90% yield.
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