Recent developments in the stereoselective synthesis of α-aminoacids

In the second half of the twentieth century much effort was invested in the preparation of highly reactive polar organometallic reagents. The high reactivity of these reagents precluded the presence of many functional groups and often good chemoselectivities and stereoselectivities could only by achieved by transmetalation reactions. The synthesis of increasingly complex target molecules and the desire to avoid tedious protection-deprotection steps has led inevitably to the use of functionalized organometallic reagents in retrosynthesis. In the last fifteen years, the generation of organic derivatives of numerous metals and metalloids (Li, Mg, B, Zn, Sn) was investigated. In this review the most important preparations and applications of organometallic reagents in organic synthesis will be covered, with particular emphasis on organozinc reagents.

New Applications of Polyfunctional Organometallic Compounds in Organic Synthesis

Polysulfone main chains have been functionalized with hypersulfonated aromatic side chains where the sulfonic acid groups were highly concentrated on a local scale, with two acid groups placed on the same aromatic ring. This molecular design was implemented to promote the nanophase separation that takes place in proton-exchange membranes between the hydrophobic polymer main chain and the hydrophilic ionic groups responsible for the water uptake and conduction. Morphological investigations revealed that polysulfones functionalized with disulfonaphthoxybenzoyl or trisulfopyrenoxybenzoyl side chains contained larger and more uniform ionic clusters, as compared to conventionally sulfonated polysulfones where the acid groups are dispersed along the main chain. Membranes based on the polymers carrying hypersulfonated side chains formed efficient networks of water-filled nanopores upon hydration, which facilitated excellent levels of proton conductivity exceeding that of the commercial Nafion membrane at moderate water uptakes.

Proton-Conducting Aromatic Polymers Carrying Hypersulfonated Side Chains for Fuel Cell Applications†

Mechanically strong and flexible membranes with very high local concentrations of immobilized proton-conducting phosphonic acid have been achieved by grafting poly(vinylphosphonic acid) side chains onto polysulfones. The graft copolymers were prepared by anionic polymerization of diethyl vinylphosphonate initiated from lithiated polysulfones, followed by quantitative cleavage of the ester functions. The resulting phosphonic acid units acted like monoprotic acids to indicate a high level of intramolecular interactions, and the phase-separated nature of the copolymers was shown by dual glass transitions. Fully polymeric membranes were conveniently cast from solution and showed high proton conductivities, e.g., 5 mS/cm under nominally dry conditions at 120 °C and up to 93 mS/cm under 100% relative humidity at the same temperature. The corresponding conductivities measured for Nafion 115 under the same conditions were 0.04 and 105 mS/cm, respectively. The former membranes furthermore showed high thermal stabi...

Polysulfones grafted with poly(vinylphosphonic acid) for highly proton conducting fuel cell membranes in the hydrated and nominally dry state

Thin layer capacitors are formed from a first flexible metal layer, a dielectric layer between about 0.03 and about 2 microns deposited thereon, and a second flexible metal layer deposited on the dielectric layer. The first flexible metal layer may either be a metal foil, such as a copper, aluminum, or nickel foil, or a metal layer deposited on a polymeric support sheet. Depositions of the layers is by or is facilitate by combustion chemical vapor deposition or controlled atmosphere chemical vapor deposition.

Formation of thin film capacitors

Titration of alkyllithiums with a simple reagent to a blue endpoint

Observations on Sn-Li exchange in α-aminoorganostannanes and the configurational stability of non-stabilized α-aminoorganolithiums

Regioselectivity in electrophilic substitution of 5-aminoindoles and 5-aminoindolines: synthesis of pyrrolo[3,2-e]indoles and isomeric pyrrolo[2,3-f]indoles

A process for making pure sodium enalapril is provided which includes the step of decomplexing essentially pure sodium enalapril-sodium iodide complex to yield essentially pure sodium enalapril.

Sodium enalapril complex and the use thereof to make sodium enalapril

An FMO Theory prediction that 5-aminoindoles, 5, should react with electrophiles preferentially at C4 rather than at C6 whereas N1-acyl-5-aminoindolines, 6, should react preferentially at C6 rather than C4 is borne out experimentally by the synthesis of a pyrrolo[3,2-e]indole from 5 and pyrrolo[2,3-f]indoles from 6.

Regioselectivity in Electrophilic Substitution of 5-Aminoindoles and 5- Aminoindolines: Synthesis of Pyrrolo(3,2-e)indoles and Isomeric Pyrrolo(2,3-f)indoles.

Andrew Burchat

Papers

Titration of alkyllithiums with a simple reagent to a blue endpoint

Observations on Sn-Li exchange in α-aminoorganostannanes and the configurational stability of non-stabilized α-aminoorganolithiums

Regioselectivity in electrophilic substitution of 5-aminoindoles and 5-aminoindolines: synthesis of pyrrolo[3,2-e]indoles and isomeric pyrrolo[2,3-f]indoles

Sodium enalapril complex and the use thereof to make sodium enalapril

Regioselectivity in Electrophilic Substitution of 5-Aminoindoles and 5- Aminoindolines: Synthesis of Pyrrolo(3,2-e)indoles and Isomeric Pyrrolo(2,3-f)indoles.