New hydrogen-bonding organocatalysts: Chiral cyclophosphazanes and phosphorus amides as catalysts for asymmetric Michael additions

• Helge Klare,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2014, 10, 224–236, doi:10.3762/bjoc.10.18

• . DFT computations reveal high hydrogen-bonding strengths of cyclodiphosphazane PV-amides compared to urea-based catalysts. Experimental results and computations on the enantiodetermining step with cis-cyclodiphosphazane 14a suggest a strong bidentate H-bond activation of the nitrostyrene substrate by

• the catalyst. Keywords: DFT computations; hydrogen bonding; Michael addition; organocatalysis; phosphazanes; Introduction Organocatalysis has gained great impact in promoting highly enantioselective [1][2][3][4] and eco-friendly [5] reactions. Within the field of organocatalysis hydrogen-bonding (HB

Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts

• Mostafa Kiamehr,
• Firouz Matloubi Moghaddam,
• Satenik Mkrtchyan,
• Volodymyr Semeniuchenko,
• Linda Supe,
• Alexander Villinger,
• Peter Langer and
• Viktor O. Iaroshenko

Beilstein J. Org. Chem. 2013, 9, 1119–1126, doi:10.3762/bjoc.9.124

• proceeds by regioselective attack of the central carbon atom of the 1,3-dicarbonyl unit to 4-position of the pyridinium salt and subsequent cyclization by base-assisted proton migration and nucleophilic addition of the oxygen atom to the 2-position, as was elucidated by DFT computations. Fairly extensive

• corroborated by X-ray [51] diffraction analysis (Supporting Information File 1, Figures S2, S3, S4) Reaction mechanism In order to shed light on the reaction mechanism we used DFT computations at the B3LYP/6-31G(d,p) [52][53][54] level, as implemented in the Gaussian 09 program [55], and acetonitrile was

Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes

• Roy T. McBurney and
• John C. Walton

Beilstein J. Org. Chem. 2013, 9, 1083–1092, doi:10.3762/bjoc.9.120

• DFT computations, which gave insights into factors influencing the two cyclisation modes. Keywords: cyclisation; EPR spectroscopy; free radicals; heterocycles; oxime carbonates; Introduction Radical cyclisations onto aromatic acceptors take place readily, even though disruption of the 6π-electron

• arm is much more flexible. This paper reports our study of the chemistry of these compounds by means of product analyses, solution EPR spectroscopy and DFT computations. We encountered an intriguing interplay between spiro-cyclisation and ortho-cyclisation of the iminyl intermediates and factors

• . The ortho-product then accumulates because of thermodynamic control. Alternatively, spiro-radical 12a might rearrange via a tetracyclic aziridinyl intermediate (or transition state) at higher temperatures. DFT computations (see below) undermined this possibility however. EPR experiments with the

Synthesis and evaluation of new guanidine-thiourea organocatalyst for the nitro-Michael reaction: Theoretical studies on mechanism and enantioselectivity

• Tatyana E. Shubina,
• Matthias Freund,
• Sebastian Schenker,
• Timothy Clark and
• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2012, 8, 1485–1498, doi:10.3762/bjoc.8.168

• -PCM), {MP2/6–31G(d)//B3PW91/6–31G(d)} and [DFT-D]. Supporting Information The Supporting Information File features data from DFT computations (computed absolute energies (Hartree) and zero-point vibrational energies (ZPVE, kcal·mol−1) at different levels of theory) as well as the respective GAUSSIAN

EPR and pulsed ENDOR study of intermediates from reactions of aromatic azides with group 13 metal trichlorides

• Giorgio Bencivenni,
• Riccardo Cesari,
• Daniele Nanni,
• Hassane El Mkami and
• John C. Walton

Beilstein J. Org. Chem. 2010, 6, 713–725, doi:10.3762/bjoc.6.84

• its electron-withdrawing substituent, did not react. In general the aromatic azides appeared to react most rapidly with AlCl3 but this reagent tended to generate much polymer. InCl3 was the least reactive group 13 halide. DFT computations of the radical cations provided corroborating evidence and

• explain the absence of the 19F high-frequency line in our spectrum. DFT computations of radical cation properties Quantum chemical calculations were carried out with the Gaussian 03 programme package [35][36]. Density functional theory with the UB3LYP functional was employed. The equilibrium geometries