Amine Protection/α-Activation with the <i>tert</i>-Butoxythiocarbonyl Group: Application to Azetidine Lithiation–Electrophilic Substitution

<i>tert</i>-Butoxythiocarbonyl (Botc), the long-neglected thiocarbonyl analogue of Boc, facilitates (unlike its alkoxycarbonyl cousin) α-lithiation and electrophile incorporation on <i>N</i>-Botc-azetidine. <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-<i>endo</i>,<i>endo</i>-Tetramethyl-2,5-diaminonorbornane proved optimal as a chiral ligand, generating adducts with er up to 92:8. Facile deprotection, under conditions that left the corresponding <i>N</i>-Boc systems intact, was achieved using either TFA or via thermolysis in ethanol.