Kinetics of the reactions of phenylketene dimethyl acetal with azocarboxylate esters

Catalytic Enantioselective Amination of Enolsilanes Using C2-Symmetric Copper(II) Complexes as Chiral Lewis Acids

“…Mechanistic Considerations. The stoichiometric [Cu(( S , S )- t -Bu-box)](OTf) 2 ( 1 )-catalyzed reaction between enolsilane 4 and azo-imide 3 in the absence of trifluoroethanol results in the rapid formation of an intermediate with an IR frequency at 1687 cm -1 , characteristic of the CN stretch in 5,6-dihydrooxadiazenes, as evidenced by in situ IR spectroscopy (Supporting Information). We propose that this intermediate is the formal hetero-Diels-Alder adduct A as its derived Cu(II) complex A-1 (Scheme ) .…”

Reactions of ketenes. XX. Phenylketene dimethylacetal as synthon for the introduction of functionalized phenylethyl units

“…ate [3,4], thiobenzoylisocyanate [5], diphenylketene [6,7] nitrile oxides [8], phenylazide [9], ethyl azidoformate [lo-121, azocarboxylate esters [13-151, ethyl diazoacetate [ 11, to give linear or cyclic gem-dimethoxy compounds which owing to the structural features are intermediates in organic synthesis [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Therefore by use of this electronrich alkene several compound types were obtained, a functionalized phenylethyl unit being introduced in the skeleton of the molecule of the reactive.…”

Reactions of ketene acetals, ketene thioacetals, and ketene aminals with ethyl benzoylazocarboxylate

“…Phenylketene dimethyl acetal reacts 50 times faster with ethyl benzoylazocarboxylate than with diethyl azodicarboxylate, in line with the predicted order. 25 However, when the energy difference between the HOMO of the dieneophile and the LUMO of the diene becomes low enough, as in the case of the reaction of l,l-di(IV-morpholinyl)ethylene and ethyl benzoylazocarboxylate, charge transfer occurs, which in this case is followed by radical cation formation. The observations that tetracyanoethylene forms radical-anion salts with tetrakis(dimethylamino)ethylene,19,20,26,27 radical cation-radical anion salts with tetramethylthioethylene,19 and charge-transfer complexes with ketene aminals28 is consistent with the high energy HOMO's of these ethylenes.…”