Activation And Transformation Of Allylic C-O,Aromatic C-S And C-N Bonds

This thesis focuses on activation and transformation of allylic C-O bonds and ar?omatic C-S and C-N bonds.We carried out the C-O bond cleavage of allyl alcohols and the C-N bond cleavage of trimethylammonium salts in the presence of nickel catalysis.We also performed the C-S bond cleavage of aryl and heteroaryl thiols under transition-metal-free conditions.Chapter 1 introduces nickel-catalyzed cross-coupling of allyl alcohols with aryl-or alkenylzinc reagents.Ni(OTf)2/dppe was demonstrated to effectively catalyze the reaction,resulting in cleavage of the C-O bonds and formation of C-C bonds.The re?action exhibits high regioselectivity.Reaction of both(E)-3-arylprop-2-en-l-ols and 1-aryl-prop-2-en-l-ols substrates results in linear coupling products.The reaction also shows good EiZ selectivity for the new C-C double bonds,(E)-geometry alkenes being formed in most cases.The catalyst system is also suited for the coupling of secondary allyl alcohols to afford regioselective coupling products with(E)-C-C double bond ge-ometry.The reaction might proceed through a Ni(0)/Ni(?)cycle.Lithium,magnesium,and zinc ions play important roles in the catalytic process.Chapter 2 presents the synthesis of allyl silanes via NiCl2(PMe3)2-catalyzed cross-coupling of allyl alcohols with silylzinc reagents.The method performs the reactions under mild conditions and can tolerate functional groups including OMe,OPh,NMe2,CF3,OCF3,OCHF2,F,Cl,SMe,CO2Me,C(O)NEt2 groups and oxygen-,nitrogen-,sulfur-contaning heterocycles.The reaction exhibits high regioselectivity,both(E)-3-arylprop-2-en-l-ols and 1-aryl-prop-2-en-l-ols resulting in linear coupling products.The reaction also shows good E/Z selectivity for the new formed C-C double bonds,(E)-geometry alkenes being formed in most cases.Chapter 3 describs transition-metal-free cross-coupling of aryl and heteroaryl thi-ols with arylzinc reagents.The reaction exhibited wide substrate scope and good com-patibility of functional groups.Electron-rich and-poor aryl or heteroaryl thiols can be converted.Various arylzinc reagents,including electron-rich and electron-poor reagents,can be employed as the coupling partners.Preliminary mechanistic studies suggest a nucleophilic aromatic substitution pathway,and Mg2+ and Li+ ions play important roles in the process of reaction.Chapter 4 reveals NiCl2(dppf)-catalyzed C-P coupling of aryl,benzyl,or allyl am-monium salts with P(O)H compounds.Through the reaction a series of phosphonylation products of the ammonium salts were synthesized in reasonable to excellent yields in most cases.The method accomodates a wide scope of substrates and tolerates a range of functional groups such as OMe,CN,CF3,F,Cl,C(O)NMe2,and C(O)tBu.The reaction might proceed through a Ni(O)/Ni(?)cycle process.