Search

Research has been conducted on the salts. Results indicate that the charge-transfer ethylenedithiotetrathiafulvalenoquinone-1,3-dithiolemethide charge-transfer salts containing FeBr (sub)4 (super)- and GaBr (sub)4 (super)- counteranions have been obtained as needle crystals with almost identical structures.

Research was conducted to examine the direct synthesis of terminal alkynes via Pd-catalyzed cross coupling of aryl and alkenyl halides with ethynylmetals containing Zn, Mg, and Sn. A critical comparison of countercations was also performed. Results indicate that the reaction of HC=CSnBu1 is generally slower and lower yielding in some difficult cases. When no significant difficulties are present, the use of comercially available HC=CMgBr should be considered because of its commercial availability, operational simplicity and relatively low cost.

Freelingyne was prepared with essentially full control of the alkene geometries. Freelingyne is a sesquiterpene from Eremophila freelingii which has a number of synthetically interesting structural subunits such as a methyl-substituted (E)-alkene and a (Z)-gamma-alkylidenebutenolide. The E and Z methyl-substituted alkene units were produced through the Zr-catalyzed carboalumination with Me3Al5 and the Cu-catalyzed methylmagnesation, respectively, of propargyl alcohol, followed by iodinolysis.

Cyclialkylation reactions involving (4-halo-1-alkenyl)metals offer a simple and efficient route to cyclobutenylmetals which are easily convertible to the corresponding iodides. Their palladium-catalyzed cross-coupling reactions, using Zn as the metal countercation, and the reaction of the iodides with alkyllithiums were also investigated. The 4-halo-1-metallo-1-butyne cyclization-cross-coupling protocol also affords a general route to 1,2-diorganylcyclobutenes.

Reactions of alkynes with organoaluminums and zirconocene derivatives require carbon-hydrogen activation to produce metallocyclic intermediates. In a study of zirconium-catalyzed carboalumination of alkynes, it was shown that C-H activation results in C-M bond addition to alkynes. The addition reactions resulted in the formation of hydrometalation products and 1,1-dimetalloalkanes in similar yields.

The palladium-catalyzed cyclization reactions of w-alkene-containing alkenyl iodides under the influence of 1-100 atm of carbon monoxide (CO) either in the presence or absence of alcohol are investigated. Results indicate that the reactions lead to three types of cyclic acylpalladation (Ac-Pd) and three types of cyclic carbopalladation processes. Type II Ac-Pd products result in the presence of alcohol at relatively high temperatures and at 1 atm of CO. A different reaction profile emerges in the absence of alcohol.

The scope of the cyclic acylpalladation reaction in palladium-catalyzed carbonylation of 1-Iodo-2-alkenylbenzenes with respect to the product ring size is investigated. The effects of carbon substituents in the parent vinyl group as well as heteroatom substituents on the reaction is evaluated. Results indicate that palladium-catalyzed carbonylation, whether with or without an external nucleophile, can produce modest yields of five and six membered cyclic acylpalladation products. Carbon substituents are shown to exert profound effects while those of heteroatom substituents are diverse and unclear.

Palladium (Pd) complexes are finding wide applicability in organic synthesis as reaction catalysts because they allow easy entry of carbon-carbon bonds and exhibit reversible interconversion between two stable oxidation states. This versatility has prodded chemists to explore the possibility of using Pd complexes in cyclization reactions. This review focuses on a new synthetic methodology for the creation of cyclic organic compounds via cyclic carbopalladation. The discussion includes examples of reactions involving carbopalladation with alkenes, alkynes, conjugated dienes and allenes.

The catalytic intramolecular carbopalladation of omega-haloallenes produces five-membered rings through twelve- and twenty-membered rings due to the high reactivity of the allenes and organopalladium species. The use of the dilute solution technique and n-Bu4NCl supports the synthesis of the eight-membered and larger rings. The reaction follows an oxidative addition- carbopalladation mechanism that creates allylpalladium intermediates.

A Pd-phosphine complex catalyzes the cyclization of allene-having aryl and alkenyl halides, producing seven- and eight-membered cycloalkanes. This method involves the formation of a carbon-carbon bond at the central carbon atom of the allene moiety. Intramolecular cyclic carbopalladation of allenes along with Diels-Alder reaction-oxidation produces fused tricyclic biaryls.

Palladium-catalyzed cross-coupling reactions involving Zn, Al, Zr (Negishi coupling) and B (Suzuki coupling) have brought revolutionary changes in organic synthesis. The synthesis of 1,3-, 1,4-, and 1,5-dienes are discussed.

A highly efficient method is reported for the synthesis of stereoisomerically pure alpha,omega-diheterofunctional reduced polypropionates, the essential features of which are represented by the conversion of inexpensive styrene into 2-methyl-4-phenyl-1-pentanol in 50% yield over two steps.

The authors review the publications on palladium-catalyzed alkynylation. The topics of interest include the preparation of terminal alkynes, the use of electron-deficient alkynes, and the mechanistic aspects of palladium-catalyzed alkynylation.

Intermolecular selective alkyne coupling with nitriles and ketones have been undertaken, and the structure of a zirconacyclopentene with a single carbon-carbon bond between its Beta and Beta' carbons is reported. This reveals that zirconacyclopentene coupling with nitriles and ketones proceeds through the Beta,Beta' carbon-carbon bond cleavage of zirconacyclopentenes. In certain reactions, zirconacyclopentenes behaved as zirconocene-alkyne compounds without phosphine.