Complete Regiochemical Control Research Articles

Synthesis of Highly Substituted Phenols and Benzenes with Complete Regiochemical Control.

Substituted phenols are requisite molecules for human health, agriculture, and diverse synthetic materials. We report a chemical synthesis of phenols, including penta-substituted phenols, that accommodates programmable substitution at any position. This method uses a one-step conversion of readily available hydroxypyrone and nitroalkene starting materials to give phenols with complete regiochemical control and in high chemical yield. Additionally, the phenols can be converted into highly and even fully substituted benzenes.

Regiospecific synthesis of neuroprotective 1,4-benzoxazine derivatives through a tandem oxidation-Diels-Alder reaction.

The tandem oxidation-inverse electron demand Diels-Alder reaction of o-aminophenol derivatives and enamines has been accomplished at room temperature using a stoichiometric amount of manganese dioxide as the oxidant to furnish highly substituted 1,4-benzoxazine cycloadducts with complete regiochemical control. Because of its efficiency in introducing diverse elements in both cycloaddition partners, this one-pot process should allow the assembly of libraries of biologically relevant 1,4-benzoxazine derivatives. In this respect, the 3,3-diphenyl-substituted-1,4-benzoxazine derivative 3n was found to be a potent neuroprotective agent in an animal model of excitotoxic lesions in newborn mice.

Three-Component Coupling Sequence for the Regiospecific Synthesis of Substituted Pyridines

A de novo synthesis of substituted pyridines is described that proceeds through nucleophilic addition of a dithiane anion to an α,β-unsaturated carbonyl followed by metallacycle-mediated union of the resulting allylic alcohol with preformed trimethylsilane-imines (generated in situ by the low-temperature reaction of lithium hexamethyldisilazide with an aldehyde) and Ag(I)- or Hg(II)-mediated ring closure. The process is useful for the convergent assembly of di- through penta-substituted pyridines with complete regiochemical control.

Regioselective Esterification and Etherification of Cellulose: A Review

Deep understanding of the structure-property relationships of polysaccharide derivatives depends on the ability to control the position of the substituents around the monosaccharide ring and along the chain. Equally important is the ability to analyze position of substitution. Historically, both synthetic control and analysis of regiochemistry have been very difficult for cellulose derivatives, as for most other polysaccharide derivatives. With the advent of cellulose solvents that are suitable for chemical transformations, it has become possible to carry out cellulose derivatization under conditions sufficiently mild to permit increasingly complete regiochemical control, particularly with regard to the position of the substituents around the anhydroglucose ring. In addition, new techniques for forming cellulose and its derivatives from monomers, either by enzyme-catalyzed processes or chemical polymerization, permit us to address new frontiers in regiochemical control. We review these exciting developments in regiocontrolled synthesis of cellulose derivatives and their implications for in-depth structure-property studies.

Regioselective Synthesis of Tetrasubstituted Pyrroles by 1,3-Dipolar Cycloaddition and Spontaneous Decarboxylation

We developed a novel regioselective synthesis of tetrasubstituted pyrroles via the classic 1,3-dipolar cycloaddition of alpha,beta-unsaturated benzofuran-3(2H)-one and azlactones (1) followed by spontaneous decarboxylation. The complete regiochemical control of tetrasubstituted pyrroles was confirmed by the orthogonal synthesis of complementary regioisomers (7a and 7b) simply by using different azlactones (1a and 1b, respectively).

ChemInform Abstract: Realization of Complete Regiochemical Control During the Conversion of Squarate Esters into Complex Linear and Angular Polyquinanes. The Consequences of Incorporating a Leaving Group into One of the Alkenyllithium Reactants.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Realization of Complete Regiochemical Control during the Conversion of Squarate Esters into Complex Linear and Angular Polyquinanes. The Consequences of Incorporating a Leaving Group into One of the Alkenyllithium Reactants

A useful method is presented for controlling whether linear or angular triquinanes are formed during a reaction cascade initiated by the 2-fold addition of alkenyl anions to diisopropyl squarate. The key feature of the process involves the incorporation of a leaving group into one of the original nucleophilic reagents. Placement of the nucleofuge within a cyclic anion leads ultimately to formation of a linear product. Extracyclic and intracyclic options are possible, with preference given to the better leaving group when a competitive situation exists. When the leaving group is incorporated into an acyclic component, angular triquinanes result instead. Several other aspects of this impressive scaffolding scheme are detailed.

Design, synthesis, and control of conducting polymer architectures: structurally homogeneous poly(3-alkylthiophenes)

The full details of a facile synthesis of structurally homogeneouspoly(3-alkylthiophene) (PAT's) is presented. In three steps from 3-bromothiophene, PAT's can be made with complete regiochemical control. We define structurally homogenous an a regiochemically well-defined polymer structure that in oar cane contains almsost exclusively head-to-tail couplings (HT-HT) (2,5-couplings between adjacent thiophene rings). By analysis of the NMR data, oar poly(n-butylthiophene) (5a) contains 93% HT-HT couplings, 98% of the desired regiochemistry is found in poly(n-hexylthiophene) (5b), 97% in poly(n-octylthiophene), (5c), and 95% in poly(n-dodecylthiophene), (5d)

Regio- and stereoselectivity of intramolecular nitrile oxide cycloaddition to furan

Intramolecular nitrile oxide cycloaddition to functionalized furans occurs with complete regiochemical control but low diastereoselectivity.

ChemInform Abstract: A Facile Route to α‐Imino Acetals and the Corresponding Monoacetal Derivatives of α‐Diketones with Complete Regiochemical Control.

AbstractThe nitriles (I) are converted to the orthoesters (III) which are coupled with pyruvonitrile (IV) to give the cyano acetals (V).

A facile route to α-imino acetals and the corresponding monoacetal derivatives of α-diketones with complete regiochemical control.

Treatment of representative orthoesters ( 2 ) with pyruvonitrile ( 3 ) afforded the corresponding α, α-diethoxynitriles ( 4 ) in 65–80% yields. Depending upon the conditions used to protonate the initial adduct, subsequent addition of an organolithium ( 5 ) or Grignard reagent to the latter ( 4 ) led to the obtention of either α-imino acetals ( 6 ) or the corresponding monoprotected α-diketones ( 7 ) in >90% yield.