Efficient Detachment of N-Benzyl Carbamate Group

Abstract

The efficient deprotection of N-benzyl carbamate (N-Cbz) group under the mild conditions with a combination of hard Lewis acid and soft nucleophile is described.

protecting groups - N-benzyl carbamate - diethylaluminium chloride - lactams - thioanisole

References

<A NAME="RY07302ST-1">1</A>

Present Address: 6-14-44 Asabu-Cho, Kita-Ku, Sapporo 001-0045, Japan

Reviews:

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<A NAME="RY07302ST-6">6</A> The respective substrates of Tables 1 and 2 were prepared by the Diels-Alder reactions of α-exomethylene lactams with the corresponding dienes: Tsujimoto T. Ishihara J. Horie M. Murai A. Synlett  2002,  399 

<A NAME="RY07302ST-7">7</A>

General Procedure: To a stirred solution of N-benzyl carbamate 1 (112 mg, 0.5 mmol) in CH₂Cl₂ (5.0 mL) was added a solution of Et₂AlCl in hexane (1.0 M solution, 0.55 mL, 0.55 mmol) at -78 °C. After 10 min, MeSPh (1.1 mmol) was added to this mixture, and the mixture was stirred at 25 °C for 1 h. The mixture was then diluted with Et₂O (5 mL), and washed with sat. aq NaHCO₃ (5 mL) and sat. brine (5 mL). The combined aq layers were extracted twice with EtOAc (5 mL). The combined extracts were dried over anhyd MgSO₄, filtered through Celite, and concentrated in vacuo. The residue was purified by chromatography (SiO₂, 50% EtOAc-hexane) to afford δ-valerolactam 2 (48 mg, 0.49 mmol, 97%) as yellow solids.

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