Comprehensive mechanistic insights into the activity of different catalysts based on different ligands are important for further ligand design and catalyst improvement. Herein, we report a combined computational and experimental study on the mechanism and catalytic activity of the ylidesubstituted phosphine Cy 3 P−C(Me)PCy 2 (keYPhos, L1) in C−N coupling reactions including a comparison with the established and often-applied phosphines Cy JohnPhos (L2) and P(tBu) 3 (L3). Density functional theory (DFT) calculations together with the possible isolation of several intermediates within the catalytic cycle demonstrate that L1 readily forms low-coordinated palladium complexes [such as L1•Pd(dba)], which easily undergo oxidative addition and subsequent amine coordination as well as reductive elimination. Due to the possible opening and closing of the P−C−P angle in L1, the steric bulk can be adjusted to the metal environment so that L1 retains its conformation throughout the whole catalytic cycle, thus leading to fast catalysis at room temperature. Comparative studies of the three ligands with Pd 2 dba 3 as a Pd source show that only L1 efficiently allows for the coupling of aryl chlorides at room temperature. DFT studies suggest that this is mainly due to the reluctance/inability of L2 and L3 to form the catalytically active species under these reaction conditions. In contrast, the YPhos ligand readily forms the prereactive complex and undergoes the first oxidative addition reaction. These observations are confirmed by kinetic studies, which indicate a short induction period for the formation of the catalytically active species of L1, followed by fast catalysis. This behavior of L1 is due to its unique electronic and steric properties, which support low activation barriers and fast catalyst generation.

s-Block metal carbenoids are carbene synthons and applied in a myriad of organic transformations. They exhibit a strong structure-activity relationship, but this is only poorly understood due to the challenging high reactivity and sensitivity of these reagents. Here, we report on systematic VT and DOSY NMR studies, XRD analyses as well as DFT calculations on a sulfoximinoyl-substituted model system to explain the pronounced solvent dependency of the carbenoid stability. While the sodium and potassium chloride carbenoids showed high stabilities independent of the solvent, the lithium carbenoid was stable at room temperature in THF but decomposed at À10 8C in toluene. These divergent stabilities could be explained by the different structures formed in solution. In contrast to simple organolithium reagents, the monomeric THF-solvate was found to be more stable than the dimer in toluene, since the latter more readily forms direct Li/Cl interactions which facilitate decomposition via a-elimination.

Background: Four members of N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates [DSTMG]n[X], where n= 1 or 2; X= FeCl4 - , Zn2Cl6 2-, NiCl4 2-, MnCl4 2- were synthesized as solid Brønsted-Lewis acidic compounds and studied the catalytic activity with the most acidic salt for three-component synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2- e][1,3]oxazin-3-ones. Methods: N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates of the four transition metal cations such as Fe(III), Zn(II), Ni(II) and Mn(II) were prepared after treatment of the parent ionic liquid N,N-disulfo-1,1,3,3- tetramethylguanidinium chloride [DSTMG][Cl] with the respective metal chlorides in different mole fractions at 75 ºC. The synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones was carried out via three-component reaction of 2-naphthol, aromatic aldehydes and urea under neat condition at 90 ºC using 7 mol% of the [DSTMG][FeCl4] catalyst. Results: The characterization of synthesized chlorometallates were done using spectroscopic and other analytical techniques including thermogravimetric analysis and Hammett acidity studies. Among the four salts, the salt of Fe(III) ion was observed as the strong Brønsted acidic hydrophobic salt and thus chosen for the catalytic study. Conclusion: A new type of chlorometallates of guanidinium cation with composition [DSTMG]n[X], where X= FeCl4 - /Zn2Cl6 2-/ NiCl4 2-/ MnCl4 2- and n= 1 or 2 were developed as –SO3H functionalized solid acids with varied thermal stability (150-250 ºC) and physisorbed water (0-20%) as observed from the thermogravimetric study. From them, the most Brønsted acidic Fe(III) salt was employed as efficient recyclable heterogeneous catalyst for the one-pot synthesis of 1,2- dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones in neat condition.

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