Acharan S. Narula

An analysis of the diastereomeric transition state interactions for stereoselective epoxidation of acyclic allylic alcohols with peroxy-acids

Abstract Consideration of the magnitude of A (1,2) and A (1,3) -strain in the transition state of the epoxidation of acyclic allylic alcohols, has powerful predictive value.

Stereoselective introduction of chiral centres in acylic precursors: a probe into the transition state for V5+-catalyzed t-butylhydroperoxide (TBHP) epoxidation of acyclic allylic alcohols and its synthetic implications.

Utility of the (Me)3Si-group for manipulating the relative energies of the diastereomeric transition states for V5+-catalyzed TBHP epoxidations of acyclic allylic alcohols is presented.

An analysis of the diastereomeric transition state interactions for the kinetic deprotonation of acyclic carbonyl derivatives with lithium diisopropylamide

Abstract Consideration of A (1,2) and A (1,3) -strain in the transition states for the deprotonation of carbonyl compounds using LDA as a base has powerful predictive value.

Tricarbonylcyclohexadienyliron complexes : synthetic equivalents of aryl cations; a facile synthesis of 2-aryl-cyclopentenones and its application towards prostaglandin analogues

Abstract Tricarbonylcyclohexadienyliron cations of type 1 are converted, by alkylation with 1,2-bis(trimethylsiloxy)-1-cyclopentene, dehydration and subsequent dehydrogenation, into specifically substituted 2-aryl-2-cyclopentenones.

Organometallic compounds in organic synthesis—XI

Abstract The concept is discussed of superimposed lateral control of reactivity, stereochemistry and structures, by attachment of complexed metal atoms to olefinic systems. This differs from classical endogenous control of synthesis by classical anionoid and cationoid groups in the skeleton, and its application has many theoretical and practical advantages. It is illustrated by considerations of reactions of substituted tricarbonylcyclohexa-l,3-dieneiron derivatives; notably the derived dienyliron salts, which are defined as equivalents of specifically substituted aryl cations or as cyclohex-2-enone cations, dependent on the structures and reaction sequences. The effects are noted of classical substituents on the positions and on the rates of reactivity of some complexed dienyl cations ; both regio- and stereospecificities are dependent on the nature of the anion involved and the conditions. Probable mechanisms are discussed. Other effects of lateral control include those on the classical reactivities of attached groups (such as hydrolysis of CO2Me) and on adjacent groups, such as stereochemistry of reduction of the 3-carbonyl in the ergosterone complex. Some useful new C-C bond-forming reactions made possible by the approach are noted.

Organometallic compounds in organic synthesis: reactions of some tricarbonylcyclohexadienyliumiron complexes with 1,2-bis(trimethylsiloxy)-1-cyclopentene. A novel route to 2-(substituted)-2-cyclopenten-1-ones.

Abstract 1,2-Bis(trimethylsiloxy)-1-cyclopentene reacts with a range of tricarbonylcyclohexadienyliumiron cations to give initially siloxy acyloins, treatment of which with MeOH-HCl gives the 2-(substituted)-2-cyclopenten-1-one in good yields (56–78%).

Organometallic compounds in organic synthesis : electrophilic reactions of some tricarbonylcyclohexadienylium-iron complexes with allyltrimethyl silanes.

Abstract Allyltrimethylsilanes react with a range of tricarbonylcyclohexadienyl-iron complexes under mild conditions to form new carbon-carbon bonds in excellent yields.

25-Azacycloartanol, a potent inhibitor of S-adenosyl-L-methionine-sterol-C-24 and C-28 methyltransferases in higher plant cells

25-azacycloartanol (1) is a potent inhibitor of S-adenosyl-L-methionine-cycloartenol-C-24-methyltransferase and of S-adenosyl-L-methionine-24-methylene lophenol-C-28-methyltransferase, two microsomal enzymes of maize (Zea mays) embryos. Addition of 1 to a suspension of bramble (Rubus fruticosus) cells grown in vitro resulted in a strong decrease of the 24-ethylsterol content and in a dramatic increase of sterols lacking an alkyl group at C-24.

Stereoselective introduction of chiral centres in acyclic precursors: a probe into the transition state of m-chloroperbenzoic (m-CPBA) acid epoxidation of acyclic allylic alcohols and its synthetic implications

Abstract The magnitude of A (1,3) -interaction far exceeds that of A (1,2) -interaction in the transition state for the organic per-acid epoxidation of acyclic allylic alcohols.

Organometallic compounds in organic synthesis. An equivalent of aromatic nucleophilic substitution by reactions of tricarbonylcyclohexadienyliumiron salts with O-silylated enolates: a novel arylation in the 2-position of carbonyl compounds.

Abstract Tricarbonylcyclohexadienyliumiron salts are synthetically equivalent to specifically substituted phenyl cations.