Regiospecific Reaction Research Articles

ChemInform Abstract: Regiospecific Reaction of Phosphaimines with a Zirconocene‐Benzyne Complex. Synthesis and Reactivity of Novel Azaphosphazirconaindans.

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.

Tetrabutylammonium Fluoride Promoted Regiospecific Reactions of Trimethylsilyl-o-Carborane with Aldehydes

Abstract Trimethylsilyl-o-carborane serves as o-carborane carbanion upon fluoride ion promoted reaction with carbonyl compounds. Thus, in the presence of tetrabutylammonium fluoride, trimethylsilyl-o-carborane undergoes facile, unprecedented, carbodesilylation with aromatic and aliphatic aldehydes.

ChemInform Abstract: A Regiospecific Reaction of Pyridazines with Vicarious Nucleophilic Substitution via Their Dicyanomethylide Derivatives.

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.

Regio-and stereospecific construction of vicinal quaternary carbons: Total synthesis of (±)-albene

A regiospecific and stereoselective total synthesis of the trisnorsesquiternene (±)-albene, via a prochiral precursor is described. The ortho ester Claisen rearrangement of the allyl alcohol, obtained in two regiospecific reactions from a Diels-Alder adduct, followed by hydrolysis of the resultant ester furnished an ene acid in a highly stereoselective manner. Anhydrous copper sulphate catalysed intramolecular cyclopropanation reaction of the diazo ketone derived from the ene acid, generated a cyclopropyl ketone. The regiospecific reductive cleavage of this cyclopropyl ketone resulted in a prochiral ketone. Finally, Shapiro reaction on the tosylhydrazone, derived from the latter ketone, furnished (±)-albene.

A regiospecific reaction of pyridazines with vicarious nucleophilic substitution via their dicyanomethylide derivatives

The phenyl(or p-tolyl)sulfonylmethyl group is introduced with complete regiospecificity to the C-4 position of 3-substituted pyridazines using vicarious nucleophilic substitution of pyridazinium dicyanomethylides.

Synthesis of 3-Acetyl-5-methoxy-1,4-naphthoquinone. A New Approach

Abstract A new and efficient synthesis for 3-acetyl-5-methoxy-1,4-naphthoquinone has been developed. The synthesis involves inter alia pyrolysis of an acetylated Diels-Alder adduct and a regiospecific Fries rearrangement reaction.

ChemInform Abstract: Cyclic Phenylboronates of Ecdysteroids as Products of Regiospecific Reaction with Phenylboronic Acid.

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.

Cyclic Phenylboronates of Ecdysteroids as Products of Regiospecific Reaction with Phenylboronic Acid

The diol system in the side-chain of ecdysteroids reacts with phenylboronic acid under formation of cyclic esters. Phenylboronates of ecdysteroids I - V were prepared. The regiospecific reaction course was confirmed by 1H NMR spectra of the products. The reaction conditions were studied for 20-hydroxyecdysone (I). The phenylboronate can be prepared in high yields even in aqueous solutions. The liberation of the ecdysteroid I from the corresponding phenylboronate VI was performed using various reagents - diols or carboxylic acids.

ChemInform Abstract: Silaheterocycles. Part 14. Regiospecific Cycloaddition Reactions of Dichloroneopentylsilene with Cyclohexa‐1,3‐diene. A Novel 7‐ Silabicyclo(4.2.0)oct‐2‐ene → 2‐Silabicyclo(2.2.2)oct‐5‐ene Rearrangement.

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.

Synthesis and properties of 5‐(1,2‐dihaloethyl)‐2′‐deoxyuridines and related analogues

AbstractThe regiospecific reaction of 5‐vinyl‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (2) with HOX (X = Cl, Br, I) yielded the corresponding 5‐(1‐hydroxy‐2‐haloethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridines 3a‐c. Alternatively, reaction of 2 with iodine monochloride in aqueous acetonitrile also afforded 5‐(1‐hydroxy‐2‐iodoethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (3c). Treatment of 5‐(1‐hydroxy‐2‐chloroethyl)‐ (3a) and 5‐(1‐hydroxy‐2‐bromoethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (3b) with DAST (Et2NSF3) in methylene chloride at ‐40° gave the respective 5‐(1‐fluoro‐2‐chloroethyl)‐ (6a, 74%) and 5‐(1‐fluoro‐2‐bromoethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (6b, 65%). In contrast, 5‐(1‐fluoro‐2‐iodoethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (6e) could not be isolated due to its facile reaction with methanol, ethanol or water to yield the corresponding 5‐(1‐methoxy‐2‐iodoethyl)‐ (6c), 5‐(1‐ethoxy‐2‐iodoethyl)‐ (6d) and 5‐(1‐hydroxy‐2‐iodoethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (3c). Treatment of 5‐(1‐hydroxy‐2‐chloroethyl)‐ (3a) and 5‐(1‐hydroxy‐2‐bromoethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (3b) with thionyl chloride yielded the respective 5‐(1,2‐dichloroethyl)‐ (6f, 85%) and 5‐(1‐chloro‐2‐bromoethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (6g, 50%), whereas a similar reaction employing the 5‐(1‐hydroxy‐2‐iodoethyl)‐ compound 3c afforded 5‐(1‐methoxy‐2‐iodoethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (6c), possibly via the unstable 5‐(1‐chloro‐2‐iodoethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine intermediate 6h. The 5‐(1‐bromo‐2‐chloroethyl)‐ (6i) and 5‐(1,2‐dibromoethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (6j) could not be isolated due to their facile conversion to the corresponding 5‐(1‐ethoxy‐2‐chloroethyl)‐ (6k) and 5‐(1‐ethoxy‐2‐bromoethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (61). Reaction of 5‐(1‐hydroxy‐2‐bromoethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (3b) with methanolic ammonia, to remove the 3′,5′‐di‐O‐acetyl groups, gave 2,3‐dihydro‐3‐hydroxy‐5‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐furano[2,3‐d]pyrimidine‐6(5H)‐one (8). In contrast, a similar reaction of 5‐(1‐fluoro‐2‐chloroethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridine (6a) yielded (E)‐5‐(2‐chlorovinyl)‐2′‐deoxyuridine (1b, 23%) and 5‐(2′‐deoxy‐β‐D‐ribofuranosyl)furano[2,3‐d]pyrimidin‐6(5H)‐one (9, 13%). The mechanisms of the substitution and elimination reactions observed for these 5‐(1,2‐dihaloethyl)‐3′,5′‐di‐O‐acetyl‐2′‐deoxyuridines are described.

Assignment of the 1H, 13C and 15N resonances in cyclodextrin nitrates by 2D NMR and the determination of the regioselectivity of the hydroxylamine‐induced denitration reactions

AbstractHexakis(2,3,6‐tri‐O‐nitro)‐α‐cyclodextrin and heptakis(2,3,6‐tri‐O‐nitro)‐β‐cyclodextrin were prepared and the complete assignment of the 1H, 13C and 15N resonance signals in each case was achieved using homonuclear shift correlation experiments, one‐bond 13C1H and three‐bond 15NOC1H heteronuclear shift correlation measurements. The denitration of these cyclodextrin nitrates by hydroxylamine in pyridine was investigated to study its selectivity in preparing partially nitrated derivatives of these cyclodextrins. The sites of denitration were determined in each case using 13C and 15N NMR and the products were completely characterized. The results indicate that denitration of these cyclodextrin nitrates is a highly regiospecific reaction occurring at the 2‐position only and giving rise to hexakis(3,6‐di‐O‐nitro)‐α‐cyclodextrin and heptakis(3,6‐di‐O‐nitro)‐β‐cyclodextrin, respectively.

ChemInform Abstract: Pseudoesters and Derivatives. Part 30. Synthesis of 5‐Substituted Furan‐2(5H)‐ones by the Regiospecific Reaction of Anions of Enaminofuranones with Electrophiles.

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.

Trifluoromethyl-p-tolyldiazomethane in 1,3-dipolar cycloaddition reactions

Trifluoromethyl-p-tolyldiazomethane (I) forms [3+2]-cycloadducts with activated alkenes and alkynes. The products of these regiospecific reactions are substituted pyrazolines (II)–(VI) and pyrazoles (VIII)–(X). Reaction of (I) with fumarates, trifluoropyruvates and allyl chloride is accompanied by elimination of N2 and formation of a 1,2-bis(trifluoromethyl)stilbene. The results obtained indicate that (I) enters only the HOMO-controlled 1,3-dipolar addition reactions.

Pseudoesters and derivatives. XXX. Synthesis of 5-substituted furan-2(5 H)-ones by the regiospecific reaction of anions of enaminofuranones with electrophiles

Reactions of lithium enolates 2a,b derived from 5-methoxy(or 5-ethylthio)-4-(pyrrolidin-1-yl)- furan-2(5 H)-ones ( 1a,b) with various electrophiles, such as alkylating agents, aldehydes, phenyl isocyanate, acyl chlorides, and trimethylsilyl chloride, occur regiospecifically to give the corresponding 5-substituted derivatives in synthetically useful yields.

An NMR study of the hydroxylamine‐induced denitration of nitrocellulose, nitroamylose and some model monosaccharide nitrate esters

AbstractThe previously known method of partial denitration of trinitrocellulose by hydroxylamine in pyridine was further investigated by NMR and applied to trinitroamylose and several other monosaccharide nitrates to study its selectivity. The sites of denitration were determined in each case using 13C and 15N NMR and, in most cases, by 2D homo‐ and hetero‐nuclear (15NOC1H and 13C1H) chemical shift correlations. The results indicate that denitration of the polysaccharide nitrates is a highly regiospecific reaction occurring at the 2‐position only, whereas with the monosaccharide nitrates denitration takes place with less selectivity, at the 4‐position predominantly, and to a lesser extent at the 3‐position.

Synthesis and biological evaluation of 5‐(1‐alkoxy‐2‐haloethyl)‐2′‐deoxyuridines and related uracil analogues

AbstractA new class of 5‐[1‐alkoxy‐2‐iodo(or 2,2‐diiodo)ethyl] derivatives of 2′‐deoxyuridine and uracil were synthesized by a regiospecific reaction of the C‐5 vinyl substituent with iodine monochloride and an alcohol. These compounds were either weak or inactive antiviral and inactive cytotoxic agents.

The electron transfer reactions of cyano substituted pyridines and quinolines with thermally generated diphenyl ketyl

AbstractElectron transfer reactions of cyano substituted pyridines and quinolines with thermally generated diphenyl ketyl are reported. When E1/2(‐) for the heterocycle is less negative than ‐2V, electron transfer occurs from the ketyl to the heterocyclic base. In some cases the products obtained from the thermal reaction are the same as those obtained from the photochemical reaction with benzophenone and alcohols. In other cases different products are formed. Two bases, 2‐pyridinecarbonitrile and 2,4‐pyridinedicarbonitrile, undergo regiospecific reactions in which the course of the reaction is determined by the acidity of the medium. A mechanism in which the heterocyclic nitrogen is involved in the substitution process at the 2 position is proposed.

The cavitand concept in the synthesis of subsite-differentiated analogs of biological [4Fe-4S/Se]2+ clusters: cluster capture reactions, ligand conformational analysis, and the structure of a trigonal [4Fe-4Se]2+ analog

The previously reported clusters [Fe 4 S 4 (Me 2 LS 3 )L'] 2− (L'=RS − , Cl − ) contain the cubane-type [Fe 4 S 4 ] 2+ core and are derived from the trithiol Me 2 L(SH) 3 (1, 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)-2,4,6-tris(p-tolylthio)benzene), with as the trianion functions as a semirigid tridentate ligand. These clusters are analogous to certain biological clusters that undergo regiospecific reactions at the differentiated Fe site. In this work, the factors that render this unique ligand effective in cluster capture are explored. The reaction [Fe 4 Se 4 (SEt) 4 ] 2− +1 yields [Fe 4 Se 4 (Me 2 LS 3 )(SEt)] 2− ; treatment of the latter cluster with 1 equiv of t-BuCOCl affords [Fe 4 Se 4 (Me 2 LS 3 )Cl] 2− (5). (Ph 4 P) 2 [5]•2DMF crystallizes in the trigonal space group P3

ChemInform Abstract: Mild, Regiospecific Hydrocarboxylation of Alkynes Catalyzed by Nickel Cyanide Under Phase‐Transfer Conditions.

Abstract Phase transfer catalyzed reaction of alkynes (e.g., phenylacetylene) with carbon monoxide, aqueous base, toluene as the organic phase, and catalytic amounts of nickel cyanide as the metal catalyst and cetyltrimethylammonium bromide as the phase transfer agent, affords unsaturated acids (e.g., atropic acid) in reasonable yields. This regiospecific reaction occurs under mild conditions.

Mild, regiospecific hydrocarboxylation of alkynes catalyzed by nickel cyanide under phase transfer conditions

Phase transfer catalyzed reaction of alkynes (e.g., phenylacetylene) with carbon monoxide, aqueous base, toluene as the organic phase, and catalytic amounts of nickel cyanide as the metal catalyst and cetyltrimethylammonium bromide as the phase transfer agent, affords unsaturated acids (e.g., atropic acid) in reasonable yields. This regiospecific reaction occurs under mild conditions.