Using hyperpolarised NMR and DFT to rationalise the unexpected hydrogenation of quinazoline to 3,4-dihydroquinazoline

TY - JOUR

T1 - Using hyperpolarised NMR and DFT to rationalise the unexpected hydrogenation of quinazoline to 3,4-dihydroquinazoline

AU - Richards, Josh E.

AU - Hooper, Alexander J.J.

AU - Bayfield, Oliver W.

AU - Cockett, Martin C.R.

AU - Dear, Gordon J.

AU - Holmes, A. Jonathon

AU - John, Richard O.

AU - Mewis, Ryan E.

AU - Pridmore, Natalie

AU - Roberts, Andy D.

AU - Whitwood, Adrian C.

AU - Duckett, Simon B.

N1 - © The Royal Society of Chemistry 2018.

PY - 2018/9/18

Y1 - 2018/9/18

N2 - PHIP and SABRE hyperpolarized NMR methods are used to follow the unexpected metal-catalysed hydrogenation of quinazoline (Qu) to 3,4-dihydroquinazoline as the sole product. A solution of [IrCl(IMes)(COD)] in dichloromethane reacts with H2 and Qu to form [IrCl(H)2(IMes)(Qu)2] (2). The addition of methanol then results in its conversion to [Ir(H)2(IMes)(Qu)3]Cl (3) which catalyses the hydrogenation reaction. Density functional theory calculations are used to rationalise a proposed outer sphere mechanism in which (3) converts to [IrCl(H)2(H2)(IMes)(Qu)2]Cl (4) and neutral [Ir(H)3(IMes)(Qu)2] (6), both of which are involved in the formation of 3,4-dihydroquinazoline via the stepwise transfer of H+ and H−, with H2 identified as the reductant. Successive ligand exchange in 3 results in the production of thermodynamically stable [Ir(H)2(IMes)(3,4-dihydroquinazoline)3]Cl (5).

AB - PHIP and SABRE hyperpolarized NMR methods are used to follow the unexpected metal-catalysed hydrogenation of quinazoline (Qu) to 3,4-dihydroquinazoline as the sole product. A solution of [IrCl(IMes)(COD)] in dichloromethane reacts with H2 and Qu to form [IrCl(H)2(IMes)(Qu)2] (2). The addition of methanol then results in its conversion to [Ir(H)2(IMes)(Qu)3]Cl (3) which catalyses the hydrogenation reaction. Density functional theory calculations are used to rationalise a proposed outer sphere mechanism in which (3) converts to [IrCl(H)2(H2)(IMes)(Qu)2]Cl (4) and neutral [Ir(H)3(IMes)(Qu)2] (6), both of which are involved in the formation of 3,4-dihydroquinazoline via the stepwise transfer of H+ and H−, with H2 identified as the reductant. Successive ligand exchange in 3 results in the production of thermodynamically stable [Ir(H)2(IMes)(3,4-dihydroquinazoline)3]Cl (5).

UR - http://www.scopus.com/inward/record.url?scp=85053323630&partnerID=8YFLogxK

U2 - 10.1039/C8CC04826F

DO - 10.1039/C8CC04826F

M3 - Article

AN - SCOPUS:85053323630

SN - 1359-7345

VL - 54

SP - 10375

EP - 10378

JO - Chemical Communications

JF - Chemical Communications

IS - 73

ER -