15673-05-9

A bulky carboxylic acid bearing one 1-adamantylmethyl and two methyl substituents at the α-position is demonstrated to work as an efficient carboxylate ligand source in Pd-catalyzed intermolecular C(sp2)-H bond arylation reactions. The reactions proceeded smoothly under mild conditions, taking advantage of the steric bulk of the carboxylate ligands.

The present invention refers to processes for catalytic reversible alkene-nitrile interconversion through controllable HCN-free transfer hydrocyanation.

An active nickel catalyst prepared in situ from a Ni(II) compound, phosphine ligand, and zinc powder was found to be an efficient catalyst system for the hydrocyanation of various alkenes using acetone cyanohydrin as a safer cyano source. The combination of NiCl2·6H2O and 1,3-bis(diphenylphosphino)propane was the most efficient catalyst precursor in DMF. Under the optimized conditions, various styrenes, heterocyclic alkenes, and aliphatic alkenes were converted to their corresponding nitriles in excellent yields.

Novel derivatives of 3-(1H-imidazol-4-yl)propanol were designed on the basis of lead compounds belonging to the carbamate or ether series possessing (partial) agonist properties on screening assays of the histamine H3 receptor. One pair of enantiomers in the series of α-methyl-branched chiral carbamates was stereoselectively prepared in high optical yields. Enantiomeric purity was checked by Mosher amide derivatives of precursors and capillary electrophoresis of the final compounds with trimethyl-β-cyclodextrin as chiral selector, and was determined to be ≥95%. The novel compounds were investigated in various histamine H3 receptor assays in vitro and in vivo. Some compounds displayed partial agonist activity on synaptosomes of rat brain cortex, whereas others exhibited antagonist properties only. Selected compounds were investigated in [125I]iodoproxyfan binding studies on the human histamine H3 receptor and showed high affinity in the nanomolar concentration range. Under in vivo conditions after oral administration to mice, some of the compounds exhibited partial or full agonist activity in the brain at low dosages. The (S)-enantiomer of one pair of chiral carbamates (9) proved to be the eutomer; thus, the (S)-enantiomer was selected for further pharmacological studies. In a peripheral in vivo test model in rats, measuring the level of inhibition of capsaicin-induced plasma extravasation, (S)-9 again proved its high oral agonist potency with full intrinsic activity (ED50 values of 0.07-0.1 mg/kg depending on tissue).

Photoinduced electron transfer (PET) from an aliphatic donor to a sensitizer and fragmentation of the radical cation leads to alkyl radicals. Radical alkylation of electron-withdrawing substituted alkenes and alkynes has been obtained in this way, and its scope has been explored. Effective sensitizers are tetramethyl pyromellitate (TMPM), 1,4-dicyanonaphthalene (in combination with biphenyl, DCN/BP), and 1,2,4,5-tetracyanobenzene. Radical precursors are tetraalkylstannanes, 2,2-dialkyldioxolanes, and, less efficiently, carboxylic acids. Steady-state and flash photolysis experiments show that escape out of cage of radical ions is the main factor determining the yield of radical formation. This is efficient with triplet sensitizers such as TMPM, while with singlet sensitizers, the use of a "cosensitizer" is required, as in the DCN/BP system. Radical cations containing primary alkyl radicals escape and fragment more efficiently than those containing tertiary radicals. The thus-formed radicals are trapped by electron-withdrawing substituted alkenes, and the relative efficiency is determined by the rate of radical addition, in accord with the proposed mechanism. Among the alkynes tested, only dimethyl acetylenedicarboxylate reacts, and the order of radical reactivity is different. It is suggested that a different mechanism operates in this case and involves assistance by the alkyne to the radical cation fragmentation.

Iodide ion promotes the free radical addition of t-BuHgI to acrylonitrile to form t-BuCH2CH(CN)HgI. A facile reaction of the adduct 1-cyanoalkyl radical with t-BuHgI2- is indicated. Further promotion is observed in the pre

3-Methylcyclohexa-1,4-diene-3-carboxylates and 2-methyl-2,5-dihydrofuran-2-carboxylates decompose to generate free alkyl radicals which have been incorporated into chain reactions producing alkyl bromides, alkene adducts and ring-closure products.

Photolysis of alkylmercury halides in the presence of electronegatively-substituted 1-alkenes yields adduct radicals [RCH2CH(EWG).] that in some cases react with RHgX to form RCH2CH(HgX)(EWG), e.g., EWG = (EtO)2PO or PhSO2. When the EWG is carbonyl or cyano, the resonance stabilized adduct radicals fail to react with the alkyl mercury halide. In these cases photolysis with RHgCl/KI in Me2SO leads to the adduct mercurial via reaction of the adduct radicals with RHgI2-. The reactions of tertiary-enolyl adduct radicals are inefficient with RHgX/KI, and disproportionation of the adduct radicals is the major reaction pathway. For secondary- or tertiary-adduct radicals the reductive alkylation products are formed in excellent yield by reaction with RHgCl and silyl hydrides in Me2SO solution in a process postulated to involve RHgH as an intermediate. The relative reactivities of a number of α,β-unsaturated systems toward t-Bu. have been measured by competitive techniques. The results demonstrate a high reactivity of s-cis enones relative to the s-trans conformers.

A method for radical addition to alkenes is reported which is based on the photosensitized oxidation of a tetraalkylstannane by an excited acceptor (A*), fragmentation of the radical cation, and addition of the thus formed radical to an electron-withdrawing substituted alkene (acrylonitrile and dimethyl maleate). Aromatic nitriles and esters can be used as the electron acceptors, and they are chosen in such a way that their radical anion (A?-) reduces the adduct (and not the educt) radical. In this way the adduct radical is reduced and protonated to yield the end product, and the acceptor functions as a nonconsumed electron transfer sensitizer. In several cases the alkylation occurs more efficiently in the presence of a secondary donor (phenanthrene or biphenyl). However, when the acceptor is too easily reduced in the ground state (as with 1,2,4,5-benzenetetracarbonitrile), coupling of the adduct radical with A?- competes with its reduction.

Reactions of organic bromides, particularly of secondary and tertiary alkyl bromides, with α,β - unsaturated carbonyl compounds and acrylonitryle in the presence of the catalytic system nickel complex-zinc result in formation of products of conjugate addition of the organic moiety of the bromide and a hydrogen atom across the C=C double bond of the unsaturated substrate.

Reductive tert-butylation of electronegatively substituted alkenes is readily achieved in Me2SO by reaction with excess t-BuHgCl/Et3SiH. Reactivity studies indicate that towards t-Bu. s-cis enones are more reactive than the s-trans conformers.

The thermal decomposition mechanism of 4,4-dimethylpentanoyl m-chlorobenzoyl peroxide and its α- and β-dideuteriated analogues is described.Product analyses and CIDNP studies suggest that all three pathways, electron transfer, radical and ionic, are operative in decomposition of these peroxides.Two pulsed-NMR techniques have been employed to eliminate distortions of CIDNP intensities arising from spin-lattice relaxation.These quantitative CIDNP studies have revealed an additional pure ionic pathway which competes with the radical pair electron transfer pathway to form rearranged reaction products.

A series of 6-alkyl- or 6-(cycloalkylalkyl)-[1,3,4]thiadiazolo[3,2-a]-1,2,3-triazolo[4,5-d]pyr imidin-9(3H)-ones 1b-o was synthesized from the corresponding 1,3,4-thiadiazol-5-amines 3b-o and the antiallergic activities of the products were evaluated. Among the compounds 6-(2-cyclohexylethyl)-[1,3,4]thiadiazolo[3,2-a]-1,2,3-triazolo[4,5-d]p yrimidin-9(3H)-one 1h, whose X-ray crystallographic stereostructure is shown, was found to be a promising new antiallergic agent, which has low toxicity and dual activity as a leukotriene D4 receptor antagonist and as an orally active mast cell stabilizer.

-

Irradiation of dicarbonyl(η5-cyclopentadienyl)iron dimer 1 or decacarbonyldimanganese (2) in the presence of alkyl halides leads to C-centered radicals which can be trapped by alkenes and yields saturated and/or unsaturated addition products.Carbon radicals are generated via halogen abstraction by the initially formed metal-centered radicals resulting from homolysis of the metal-metal bond of dimeric mediators 1 and 2.No reaction occurs using octacarbonyl dicobalt (3).

Irradiation of benzyldicarbonyl(η5-cyclopentadienyl)iron complex (2) leads to homolytic cleavage of the Fe-C bond.In the presence of activated alkenes, radical addition occurs, and both saturated and unsaturated addition products 7-9 are formed.Photolysis of alkyliron complexes 2, 3, and 20 in the presence of acrylonitrile leads to the same products as the irradiation of the respective acyliron complexes 28-30.This indicates that, under photolytical conditions, alkyl and acyl complexes are in equilibrium with each other.

Tris(trimethylsilyl)silane is an effective mediator for the formation of carbon-carbon bonds via radicals using alkyl isocyanides as precursors.

Irradiation of dimeric iron complex 1 in the presence of alkyl halides yields alkyl radicals that are useful in organic synthesis.

Terminal alkenes are converted into one-carbon homologated primary alkanenitriles in high yields via hydroboration followed by a reaction with copper(I) cyanide, copper(II) acetate, and copper(II) acetylacetonate.

The reductive alkylation of acrylonitrile and of 2-cyclohexen-1-one by alkyl halides using tributylgermanium hydride was systematically evaluated.The performance of the germanium reagent was compared to that of the more commonly employed tributyltin hydride.For certain applications thegermanium reagent afforded improved yields without the use of large excess olefin concentrations.Disadvantages of the germanium reagent include a tendency to hydrogermylate active terminal olefins and a general low reactivity towards alkyl halide substrates.The following series of six other triorganotin and triorganogermanium hydrides were also briefly screened for possible application to reductive alkylations: trimesityltin hydride, trimesitylgermanium hydride, triphenyltin hydride, triphenylgermanium hydride, trineopentyltin hydride, and tricyclohexylgermanium hydride.

A convenient method for the anti-Markovnikov hydrocyanation of olefins utilizing organozirconium chemistry has been developed.This method has been shown to tolerate a wide range of functionality in the substrate olefin.

-

Reactions of (E)-3,3-dimethyl(1,2-D2)but-1-ene with hydrogen cyanide and of (E)-3,3-dimethyl(1-D)but-1-ene with deuterium cyanide have been shown to proceed in a completely stereospecific cis fashion when a catalyst system based on Pd(diop)2 was used.Reaction between 4-t-butylcyclohexene and deuterium cyanide with the catalyst system gave only the equatorial nitriles trans-4-t-butylcyclohexane-1-carbonitrile and cis-3-t-butylcyclohexane-1-carbonitrile with cis incorporation of deuterium.Use of a catalyst system based on Ni4 and zinc chloride led to significant amounts of isotopic exchange and rearrangement.These results are compared with those from hydroformylation of the olefins, and the mechanism of hydrocyanation is discussed

3-Amino-5-(t-butyl)isoxazole, in optimum yield, is prepared in a stepwise manner by reacting a lower alkyl pivalate and acetonitrile in the presence of a base to yield pivalyl acetonitrile, which in turn is allowed to react with hydroxylamine under controlled conditions of pH to yield the desired compound. The compound is a useful intermediate for the preparation of isoxazole derivatives having utility as herbicides.

-

The compounds of this invention are novel alkanimidoylthioureas having antifertility activity. They are prepared by the reaction of appropriate alkanamidines with appropriate isothiocyanates.