By using α-cyanostilbenes as Lewis acids, Lewis acidity scales have been established in ethanolic and methanolic dimethyl sulfoxide containing the appropriate 0.01 M sodium alkoxide and in the system sodium methoxide – methanol. This scale, designated [Formula: see text], describes the ability of the solvent to add an alkoxide ion to an alkene. The [Formula: see text] values range from 11.73 in methanol to 21.74 in 93.27 mole % dimethyl sulfoxide in ethanol.The most acidic indicator used to establish the scale was α-cyano-2,4-dinitrostilbene, with a pKA of 12.73 in dimethyl sulfoxide – methanol. The least acidic was α-cyano-3-trifluoro-methylstilbene, with a pKA of 21.98 in dimethyl sulfoxide – ethanol.The increase in the system's ability to add alkoxide ion to the cyanostilbenes as the dimethyl sulfoxide concentration rises is ascribed chiefly to its effect on the activity of the alkoxide ion. The functions H− and [Formula: see text], unlike their analogues in acid systems (H0 and Hr), do not diverge greatly as the concentration of the hydroxylic solvent component is decreased.

In connectio~l with other studies it was of interest to get a n estimate of the relative ground-state n-electron densities a t the 2-and 6-positions of 3-picoline and its complex with a simple metallic salt. Smith and Schneider (1) receiltly estimated the charge distribution in pyridiniu~n ion, assuming a simple proportionality between the proton resonance displacement and the electron charge deficiency on the carbon atoll1 t o which the proton is bonded. 3-Picoline-2d, 3-picoline-Gd, and their zinc chloride complexes have been prepared and their n.m.r. and infrared spectra compared.Bal;, Hansen, and Rastrup-Andersen (2) obtained pyridine-2d by the action of zinc dust and sulphuric acid-dz on 2-bromopyridine. I t was prepared more conveniently here from 2-pyridyllithium and deuterium oxide. Preliminary experiments indicated that there was no loss of deuterium when the pyridine-2d was extracted with lnineral acid instead of being isolated as the mercuric chloride complex. This is in agreement with the recent finding by Icatritzky and Ridgewell (3) that pyridine is very resistant t o proton exchange. In the same way, 3-picoline-2d, 3-picoline-Gd, and the corresponding tritiated cornpouilds were obtained (the latter by using tritiated water).The n.1n.r. spectra were run in acetonitrile solutions of the compounds, due t o the limited solubility of the zinc chloride coi~~plexes in carbon tetrachloride and to interference by chloroform when it was used. The results are summarized in Table I. 'The accuracy is f 2 cycles/sec. (4)) and its zinc chloride complex the signals for the 2-and 6-protons overlap and no resolution is possible a t 60 Nc/s. T h e shift between these two protons is seen to be +2.5 cycles/sec fro111 the spectra of 3-picoline-Gd and 3-picoline-2d respectively. From these values, the differences in n-eleciron densities are esti~nated t o be very small. Complexing, as expected, gives rise t o appreciable changes in cl~emical shift, particularly a t the /3-and r-protons. T h e corresponding shift t o lower field of the a-proton is appreciably smaller. This is probably d~~e

The rates of the base-catalyzed isomerization of a-cyano-cis-stilbenes were measured in methanolic and ethanolic dimethyl sulphoxide (DMSO) containing the appropriate 0.01 M-alkoxide as base ; the logarithms of the first-order rate constants were found to correlate with the H,acidity function. The slopes range from 0.426 to 0.665 depending on the substituent present in the a-phenyl ring and the solvent system and were shown to be related to the structure of the transition state.The effect of substituents on the rate of isomerization has been examined. Substituents in the a-phenyl ring produce effects on the rates which correlate with U-values and yield p-values of +3.07 in DMSO-ethanol and +2.82 in DMSO-methanol.The activation parameters for the isomerization reaction of three substituted a-cyano-cis-stilbenes were determined in DMSO-methanol solutions. The enthalpies of activation were in the range 14.3-1 6.7 kcal. mole-l and the entropies of activation ranged from -9.3 to -1 3.7 e.u.The mechanism of isomerization is believed to involve rate-controlling attack of alkoxide ion on the P-carbon atom of the cis-stilbene to form a carbanion in which free rotation can occur. Elimination of alkoxide ion gives the trans isomer.

The effect of substituents in the two aromatic rings of α-cyanostilbene on the Lewis acidities of these compounds towards alkoxide ions has been examined. Substituents in the β ring produce effects on the acidity which correlate with the σ values of the substituents and yield an average ρ value of + 2.22. Substituents in the α ring, however, are correlated by the σ− values and yield an average ρ value of + 4.62. A p-nitro group in the α ring exhibits a greatly enhanced σ− value (+ 1.73).

Sequential Multicomponent reactions and a Cu-Mediated Rearrangement: Diastereoselective synthesis of Tricyclic Ketones. -The first diastereoselective Cu-mediated rearrangement of bisamides containing a thiazolidiene substructure is reported which provides complex heterotricyclic annulated and bridged systems consisting of an imidazolidin-4-one and a thiomorpholine cycle. -(KROEGER, D.; FRANZ, M.; SCHMIDTMANN, M.; MARTENS*, J.; Org. Lett. 17 (2015) 23, 5866-5869, http://dx.