Al/N-based active Lewis pairs: isocyanate insertion products as efficient nucleophiles employed for the facile generation of highly functional molecules

Abstract

<jats:title>Abstract</jats:title><jats:p>The previously reported active Lewis pair (ALP) <jats:sup><jats:italic>i</jats:italic></jats:sup>Bu<jats:sub>2</jats:sub>Al–N(2-Ad)NC<jats:sub>5</jats:sub>H<jats:sub>10</jats:sub> (<jats:bold>1</jats:bold>) (2-Ad = 2-adamantyl) is readily accessible by hydroalumination of the hydrazone H<jats:sub>10</jats:sub>C<jats:sub>5</jats:sub>N–N=(2-C<jats:sub>10</jats:sub>H<jats:sub>14</jats:sub>) with H–Al<jats:sup><jats:italic>i</jats:italic></jats:sup>Bu<jats:sub>2</jats:sub>. Treatment of <jats:bold>1</jats:bold> with two equivalents of isocyanates R-N=C=O yields six-membered AlC<jats:sub>2</jats:sub>N<jats:sub>2</jats:sub>O heterocycles <jats:bold>2</jats:bold> (<jats:bold>2a</jats:bold>, R = Ph; <jats:bold>2b</jats:bold>, R = <jats:italic>p</jats:italic>-Tol) by dual insertion into the Al–N bonds. <jats:bold>2a</jats:bold> reacts as a nucleophile with carboxylic acid chlorides R-C(O)–Cl [R = CH<jats:sub>2</jats:sub><jats:sup><jats:italic>t</jats:italic></jats:sup>Bu, <jats:italic>p</jats:italic>-Tol, H<jats:sub>2</jats:sub>CCH(Me)C<jats:sub>6</jats:sub>H<jats:sub>4</jats:sub>(4-CH<jats:sub>2</jats:sub>CHMe<jats:sub>2</jats:sub>) (Ibu-profen acid chloride), 0.5 (1,4-C<jats:sub>6</jats:sub>H<jats:sub>4</jats:sub>)] to afford by elimination of <jats:sup><jats:italic>i</jats:italic></jats:sup>Bu<jats:sub>2</jats:sub>AlCl and hydrolysis new triuret derivatives R-C(O)[N(Ph)C(O)]<jats:sub>2</jats:sub>–N(2-Ad)NC<jats:sub>5</jats:sub>H<jats:sub>10</jats:sub> (<jats:bold>3a</jats:bold> to <jats:bold>3d</jats:bold>) as colourless, sparingly soluble solids in moderate (<jats:bold>3c</jats:bold>) to high (<jats:bold>3b</jats:bold>) yields. The analogous reaction of <jats:bold>2a</jats:bold> with (<jats:italic>p</jats:italic>-Tol)–C(Cl)=N(<jats:italic>p</jats:italic>-Tol) leads to the imidoyl derivative (<jats:italic>p</jats:italic>-Tol)N=C(<jats:italic>p</jats:italic>-Tol)[N(Ph)C(O)]<jats:sub>2</jats:sub>–N(2-Ad)NC<jats:sub>5</jats:sub>H<jats:sub>10</jats:sub> (<jats:bold>4a</jats:bold>), which showed a fast exchange of phenyl and tolyl groups to yield a mixture of isomers. The analogous reaction of <jats:bold>2b</jats:bold> affords the corresponding compound <jats:bold>4b</jats:bold> for which a single isomer is isolated despite the scrambling of substituents.</jats:p>