Wayne F. K. Schnatter

Electrophilic aromatic substitution: enthalpies of hydrogenation of the ring determine reactivities of C6H5X. The direction of the C6H5-X bond dipole determines orientation of the substitution.

There are still some secrets left to this well-studied reaction. Previously unreported relationships discovered are as follows. The ordering of reactivities of C6H5X is the same as that of enthalpies of hydrogenation of the ring to the correspondingly substituted cyclohexane. The orientation of substitution (meta or ortho/para) is controlled by the dipole direction of the ipso-C-X bond, like an ON/OFF switch. The difference between the halogens and other deactivating groups is that the bond between the atom bonded to the ipso carbon has the positive end of the dipole on the ipso carbon for the halogens (C(δ+)-X(δ-)) but in the opposite direction (C(δ-)-X(δ+)) for other deactivating groups. This reverses the directing effect. For all X, including the halogens, ipso-C(δ+)-X(δ-) results in ortho/para substitution. p-(13)C NMR shifts of C6H5X greater than that of benzene predict meta substitution. A linear relationship exists between p-(13)C NMR shift and ΔHhyd, except for X = halogen. With halobenzenes, the ortho/para ratios of the products are linearly related to the ipso/ortho ratios of the (13)C shifts of C6H5X for chlorinations, brominations, nitrations, and protonations. The relative reactivities of the halobenzenes are linearly related to the p-(13)C NMR shifts. The electronegativities of X are linearly related to the (13)C NMR shifts of the ipso carbon.

The synthesis of a porphyrin with a hydrocarbon encapsulated face

Abstract The uniquely hydrocarbon-like capped porphyrin (C70H68N4), 1i, has been successfully prepared by a high dilution reaction of pyrrole with tetrakis-1,2,4,5-[pentyl-5′-(2″-formylphenyl)]-benzene 1h in the presence of boron trifluoride etherate. The aldehyde 1h was prepared by four simultaneous Wittig condensations of a phosphonium salt, 1e, with 1,2,4,5-tetraformylbenzene, followed by reduction of the double bonds with Raney nickel and deprotection with perchloric acid.

Electrophilic Addition to Alkenes: The Relation between Reactivity and Enthalpy of Hydrogenation: Regioselectivity is Determined by the Stability of the Two Conceivable Products.

Although electrophilic addition to alkenes has been well studied, some secrets still remain. Halogenations, hydrohalogenations, halohydrin formations, hydrations, epoxidations, other oxidations, carbene additions, and ozonolyses are investigated to elucidate the relation of alkene reactivities with their enthalpies of hydrogenation (ΔHhyd ). For addition of electrophiles to unconjugated hydrocarbon alkenes, ln(k) is a linear function of ΔHhyd , where k is the rate constant. Linear correlation coefficients are about 0.98 or greater. None of the many previously proposed correlations of ln(k) with the properties of alkenes or with linear free-energy relationships match the generality and accuracy of the simple linear relationship found herein. A notable exception is acid-catalyzed hydration in water or in solvents stabilizing relatively stable carbocation intermediates (e.g., tertiary, benzylic, or allylic). (13) C NMR chemical shifts of the two alkene carbons also predict regioselectivity. These effects have not been noted previously and are operative in general, including addition to heteroatom-substituted alkenes.

Reactions of Cyclopropylcarbene-Chromium Complexes

Abstract The reactions of Fischer-carbene complexes containing a cyclopropane ring as one of the carbene substituents have been examined. Reaction of these complexes with alkynes leads to cyclopentenone derivatives in good-excellent yields. The reaction proceeds through a cyclopentadienone intermediate, which is reduced to the corresponding cyclopentenone derivative by chromium (0) and water. The cyclopropane ring opens at a relatively late stage of the reaction with alkynes, and does not occur until after insertion of the alkyne. Cyclopropylcarbene complexes having an alkenyl substituent at the 2-position of the cyclopropane ring undergo facile ring expansion reactions. The cyclopropane ring-opening steps of these reactions resemble classical pericyclic organic reactions, and thus the reactivity of these systems has been attributed to orbital symmetry considerations.

Coupling of Geminal Dihalides with Disodium Tetracarbonyl Ferrate: a Novel Reactivity Pattern for Collman's Reagent

The reaction of gem-dihalides with Na2Fe(CO)4 results in the formation of alkenes instead of the iron(0) carbene complexes.

A Practical Synthesis of 2,6-Dicarboxyfluorenone

Herein, we report a new and efficient method for the large scale synthesis of 2,6-dicarboxyfluorenone 5 in 95% yield using 0.01mol% of bis(triphenylphosphine)palladium(II) chloride, (PPh3)2 PdCl2, as a catalyst, starting with the reaction of 2,5-dimethylbromobenzene and 4-bromotoluene to give 2,4,5-trimethylbiphenyl 3, followed by oxidation and then cyclization.