Enantiomerically Pure N Chirally Substituted 1,3-Benzazaphospholes: Synthesis, Reactivity toward <i>t</i>BuLi, and Conversion to Functionalized Benzazaphospholes and Catalytically Useful Dihydrobenzazaphospholes

Catalytic C–P coupling of chiral <i>o</i>-bromoanilines <b>1a</b>–<b>c</b> to the corresponding <i>o</i>-phosphonoanilines <b>2a</b>–<b>c</b>, reduction to the phosphines <b>3a</b>–<b>c</b>, and final acid-catalyzed cyclocondensation represents a convenient access to the title compounds <b>4a</b>–<b>c</b>. Reaction of <b>4a</b>,<b>b</b> with <i>t</i>BuLi allows solvent-dependent directed lithiation leading either to 2-lithiobenz­azaphospholes with a −PCLi–NR– substructure (in Et₂O/KO<i>t</i>Bu), in the case of anisyl substitution accompanied by partial additional lithiation in <i>o</i>-position of the MeO-group, or to regiospecific “normal” addition with formation of −P­(<i>t</i>Bu)–CHLi–NR– species. These were trapped by ClSiMe₃, CO₂, or MeOH to give the corresponding substitution products <b>7b</b>, <b>8b</b>, <b>10b</b>, <b>11a</b>,<b>b</b> and <b>12a</b>,<b>b</b>, respectively. <b>12a</b>,<b>b</b>, containing the P–C–COOH structural unit, forms with Ni­(COD)₂ in THF very efficient ethylene oligomerization catalysts with high selectivity for linear α-olefins. The structure elucidation of the products is based on conclusive solution NMR data and crystal structure analyses of the 1-(1<i>S</i>)-anisylethyl compounds <b>3b</b> and <b>4b</b>

Enantiomerically Pure N Chirally Substituted 1,3-Benzazaphospholes: Synthesis, Reactivity toward <i>t</i>BuLi, and Conversion to Functionalized Benzazaphospholes and Catalytically Useful Dihydrobenzazaphospholes

Catalytic C–P coupling of chiral <i>o</i>-bromoanilines <b>1a</b>–<b>c</b> to the corresponding <i>o</i>-phosphonoanilines <b>2a</b>–<b>c</b>, reduction to the phosphines <b>3a</b>–<b>c</b>, and final acid-catalyzed cyclocondensation represents a convenient access to the title compounds <b>4a</b>–<b>c</b>. Reaction of <b>4a</b>,<b>b</b> with <i>t</i>BuLi allows solvent-dependent directed lithiation leading either to 2-lithiobenz­azaphospholes with a −PCLi–NR– substructure (in Et₂O/KO<i>t</i>Bu), in the case of anisyl substitution accompanied by partial additional lithiation in <i>o</i>-position of the MeO-group, or to regiospecific “normal” addition with formation of −P­(<i>t</i>Bu)–CHLi–NR– species. These were trapped by ClSiMe₃, CO₂, or MeOH to give the corresponding substitution products <b>7b</b>, <b>8b</b>, <b>10b</b>, <b>11a</b>,<b>b</b> and <b>12a</b>,<b>b</b>, respectively. <b>12a</b>,<b>b</b>, containing the P–C–COOH structural unit, forms with Ni­(COD)₂ in THF very efficient ethylene oligomerization catalysts with high selectivity for linear α-olefins. The structure elucidation of the products is based on conclusive solution NMR data and crystal structure analyses of the 1-(1<i>S</i>)-anisylethyl compounds <b>3b</b> and <b>4b</b>