Donald J. Burton

A facile synthesis of diynes

Abstract Terminal alkynes undergo self-coupling reactions in the presence of palladium bis(triphenyl phosphine) dichloride, copper(I) iodide iodine and diisopropyl amine to give the corresponding diynes in good yields.

Preparation of perfluorocarbon polymers containing phosphonic acid groups

Abstract Several co- and ter-fluoropolymers based on tetrafluoroethylene (TFE) and perfluorovinylethers, such as CF2=CFO(CF2)2P(O) (OC2H5)2, CF2=CFO(CF2)3P(O)(OC2H5)2, CF2=CFOCF2CF(CF3)O(CF2)2P(O)(OC2H5)2 and CF2=CFOC3F7, were synthesized via redox-initiated emulsion polymerization. The products were subjected to acid hydrolysis and the corresponding fluorinated polymeric phosphonic acids were obtained. Both the polymeric phosphonates and phosphonic acids can be readily processed into films by compression molding. Perfluorinated phosphonic acid membranes with an ion-exchange capacity (IEC) within the range 2.5–3.5 milliequivalents per gram and a thermal stability of 300–350 °C were prepared. The characteristics of these acid membranes were explored, and these films show promising electrochemical properties, such as proton conductivity.

A facile, general route to perfluoroalkyl allenes

Abstract Perfluoroalkyl copper reagents react with propargyl halides or tosylates in DMF or DMSO at 0°C-RT to afford perfluoroalkyl allenes regiospecifically in good yield.

A facile and general preparation of α,α-difluoro benzylic phosphonates by the CuCl promoted coupling reaction of the (diethylphosphonyl)difluoromethylcadmium reagent with aryl lodides

Abstract A series of α,α-difluorobenzylic phosphonates have been prepared in good yield (65–88%) by the CuCl promoted coupling reaction of the (diethylphosphonyl)difluoromethylcadmium reagent with aryl iodides.

The stereospecific preparation of fluorinated vinyl zinc reagents from polyfluorinated vinyl iodides or bromides and zinc metal

Abstract Fluorinated vinyl zinc reagents can be prepared readily via the direct reaction of polyfluorinated vinyl iodides or bromides with zinc metal in a variety of solvents, such as DMF, DMAc, THF, glymes, and acetonitrile. The formation of symmetrical dienes via coupling of the vinyl halide is not observed. With E and Z -vinyl subtrates total retention of configuration is observed in the formation of the zinc reagents, and in subsequent functionalization reactions. The excellent thermal stability of these zinc reagents at or above room temperature, and the possibility of employing a variety of solvents allow subsequent reactions to be easily tailored to meet experimental requirements. Therefore, this approach provides a facile, easily scaled up, stereospecific, one-pot procedure to these stable vinyl organometallic reagents.

Palladium catalyzed coupling of F-cinyl zinc reagents with aryl iodides. An improved synthesis of α,β,β-trifluorostyrenes and the stereospecific preparation of 1-phenyl-F-propenes

Abstract Palladium catalyzed coupling of trifluorovinyl zinc reagents with substituted aryl iodides provides a practical high yield route to α,β,β- trifluorostyrenes. Ortho, meta, and para substituted aryl iodides all work equally well. Similar coupling with E - and Z -1-iodo- F -propenes outlines the first stereospecific preparative route to 1-aryl- F -olefins. This approach provides a rapid, easily scaled-up synthesis via a one pot procedure to these valuable styrenes from commercially available precursors without recourse to low temperature processes or the use of unstable reaction intermediates.

Preparation, stability, reactivity and synthetic utility of a cadmium stabilized complex of difluoromethylene phosphonic acid ester

Abstract Diethyl bromodifluoromethyl phosphonate reacts readily with cadmium metal to form a stable cadmium complex. Depending on solvent, this functionalized organocadmium reagent exhibits stability for days to months. It reacts with a variety of electrophiles and serves as a synthetically useful source for the introduction of the difluoromethylene phosphonate group into organic compounds. The synthetic utility of a wide variety of fluoromethylene phosphonium ylides has been a major effort in our laboratory over the past several years [1]. The generation and capture of difluoromethylene ylides ( 1 ) as a general route to difluoromethylene olefins has been of especial interest to us [2]. In an effort to increase the nucleophilicity of the ylide, we have attempted to prepare the analogous phosphonate ylide ( 2 ). Although we have achieved modest success [3] by insitu capture of ( 2 ) in the reaction of sodium dialkyl phosphites with diethyl bromodifluoromethylphosphonate ( 3 ), attempts to pregenerate ( 2 ), either from diethyl difluoromethylphosphonate ( 4 ) or ( 3 ), have met with little success. ( 2 ) appears to have minimal stability even at low temperatures, and scale up processes of synthetic value would seem to be difficult.

The stereoselective preparation of cis and trans-1,2-difluoroethylene synthons

Abstract Isomerization of ( Z )-HFC=CFSiEt 3 with ultraviolet light and catalytic phenyl disulfide has resulted in a high yield, stereoselective preparation of cis -1,2-difluorotriethylsilylethylene, ( E )-HFC=CFSiEt 3 . ( E )-HFC=CFSiEt 3 has been converted to ( Z )-F(Bu 3 Sn)C=CFSiEt 3 , ( Z )-IFC=CFSiEt 3 , ( Z )-BrFC=CFSiEt 3 , ( Z )-Me 3 SiFC=CFSiEt 3 , and ( Z )-IFC=CFI. ( E )-IFC=CFI has been prepared from ( Z )-HFC=CFSiEt 3 .

Fluorinated Organometallic Compounds

Recent preparation of various types of fluorinated organometallic reagents is described, including perfluoroalkyl, perfluoroalkenyl, perfluoroaryl, carboalkoxydifluoromethylene, dialkoxyphosphinylidifluoromethyl and α,α-difluoroallyl and α,α-difluoropropargyl organometallics. Application of these reagents for the preparation of fluorine-containing compounds is presented with typical illustrative examples. Emphasis is focused on preparations and applications described during the past ten years.

Generation of trifluoromethylcopper from chlorodifluoroacetate

Abstract In the presence of fluoride ion, methyl chlorodifluoroacetate undergoes halide ion-promoteddecarboxylation to give trifluoromethide which can be trapped with cuprous iodide. Theresulting trifluoromethyl copper reagent has been observed spectroscopically and can betrapped with aryl iodides to give the corresponding trifluoromethylaromatic compound.