Search results for "Nucleophilic addition"

ChemInform Abstract: Stereoselective Nucleophilic Addition Reactions of Reactive Pseudopeptides.

2010

Comparative chemistry of 18-electron Mo(II) and 17-electron Mo(III) compounds containing only carbon-based ligands

1998

International audience; The chemical reactivity of various kinetically stable isomers of compound CpMo(η3-C3H5)(η4-C4H6), 1, and its oxidation product [1]+, as well as the bis-allyl Mo(III) complex CpMo(η3-C3H5)2, 2, and the bis-diene Mo(II) complex [CpMo(η4-C4H6)2]+, 3, is reviewed. The inertness toward isomerization processes of the allyl and butadiene ligands in the Mo(II) complexes has allowed a study of the relative reactivity toward both electrophilic and nucleophilic addition processes as a function of coordination mode. The dependence of various reaction pathways on the metal oxidation state has also been investigated. Of particular interest is the discovery that the electronically …

Cyclopentadienylmolybdenum(II) and -(III) complexes containing diene and allyl ligands. Part 4. Reactivity studies of the bisallyl complex CpMo(supin…

1998

Abstract Compound CpMo( η 3 -C 3 H 5 ) 2 , 3, has been synthesized from CpMoCl 4 and four equivalents of allylmagnesium bromide. While the compound is stable in donor solvents at room temperature, warming in refluxing MeCN induces the formation of 1,5-hexadiene by a metal-mediated allyl-allyl coupling process. Treatment of 3 with Bu t NC at room temperature affords CpMo( η 3 -C 3 H 5 )(Bu t NC) 2 , 4. A similar reduction with presumed allyl radical loss occurs for [CpMo( η 3 -C 3 H 5 )( η 4 -C 4 H 6 )] + , [1c] + , to afford [CpMo( η 4 -C 4 H 6 )(Bu t NC) 2 ] + , 5. Treatment of [1c] + with methyllithium affords two products, the major one (1c) corresponding to the one-electron reduction pa…

Efficient Addition of Acid Enediolates to Epoxides

2004

We report new conditions to facilitate the addition of dianions of carboxylic acids to epoxides as an alternative method to the use of aluminum enolates. These conditions require the use of a sub-stoichiometric (10%) amount of amine for dianion generation and the previous activation of the epoxide with LiCl. Other Lewis acids have been shown to be less effective. Yields are good but only low diastereoselectivity is attained, which has not been controlled despite attempts at optimization. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Reactions of platinum(iv)-bound nitriles with isomeric nitroanilines: addition vs. substitution

2012

The platinum(IV) complex trans-[PtCl(4)(EtCN)(2)] reacts smoothly and under mild conditions with isomeric o-, m- and p-nitroanilines (NAs) yielding two different types of products depending on the NA isomer, viz. the nitroaniline complexes cis/trans-[PtCl(4)(NA)(2)] (cis/trans-1-3) and the amidine species trans-[PtCl(4){NH=C(Et)NHC(6)H(4)NO(2)-m}(EtCN)] (4), trans-[PtCl(4){NH=C(Et)NHC(6)H(4)NO(2)-m}(2)] (5) and trans-[PtCl(4){NH=C(Et)NHC(6)H(4)NO(2)-p}(EtCN)] (6). Complexes 4 and 5 undergo cyclometalation, furnishing mer-[PtCl(3){NH=C(Et)NHC(6)H(3)NO(2)-m}(EtCN)] (7) and mer-[PtCl(3){NH=C(Et)NHC(6)H(4)NO(2)-m}{NH=C(Et)NHC(6)H(3)NO(2)-m}] (8), respectively. Moreover, 8 both in the solid stat…

Solution-, solid-phase, and fluorous synthesis of beta,beta-difluorinated cyclic quaternary alpha-amino acid derivatives: a comparative study.

2008

The diastereoselective synthesis of cyclic beta,beta-difluorinated alpha-amino acid derivatives bearing a quaternary stereocenter is described. The process relies on the chemo- and diastereoselective addition of allylic organometallic reagents to fluorinated alpha-imino esters and a subsequent ring-closing metathesis reaction (RCM). Complete selectivity in the nucleophilic addition was achieved with (R)-phenylglycinol methyl ether as a chiral auxiliary. The resulting amino acids were introduced into peptide chains, which could facilitate the preparation of potentially bioactive dipeptide derivatives. In addition, the solution synthesis of these cyclic fluorinated alpha-amino acids was succe…

Iron-Catalyzed C(sp2)–C(sp3) Cross-Coupling of Aryl Chlorobenzoates with Alkyl Grignard Reagents

2020

Aryl benzoates are compounds of high importance in organic synthesis. Herein, we report the iron-catalyzed C(sp2)&ndash

Studies on Adduct Formation of (+)-Anti-Benzo[a]pyrene 7,8-Dihydrodiol 9,10-Epoxide with the oligonucleotides 5′-d(CCTATCGTTATCC) and 5′-d(CCTATm5CGT…

1999

Abstract Adduct formation of (+)-anti-benzo[a]pyrene 7,8-dihydrodiol 9,10-epoxide [BPDE] and 5′-d(CCTATCGTTATCC) or 5′-d(CCTATm5CGTTATCC) (G = binding target) has been studied. The extent of trans-BPDE-N2-dG adduct formation was higher in the oligonucleotide with 5′-d(m5CG) sequence context in both single- and double stranded form compared to the non-methylated analogue. The stimulating effect of m5dC on adduct formation has previously been demonstrated in other experimental systems. The increase in yield could possibly be rationalized in terms of prestacking of the pyrenyl ring with the nucleobases prior to the nucleophilic addition. In the present study, both UV absorption and induced cir…

Back Cover Picture: Coupling of Azomethine Ylides with Nitrilium Derivatives ofcloso-Decaborate Clusters: A Synthetic and Theoretical Study (ChemPlus…

2012

Lack of nucleophilic addition in the isoxazole and pyrazole diketone modified analogs of curcumin; implications for their antitumor and chemosensitiz…

2009

Curcumin (CUR) can be considered as a good lead compound for the design of new anticancer drugs. Further, structure-activity relationship studies may clarify the importance of the redox activities in the antitumor effects of the drug. We have elaborated the alpha,beta-unsaturated 1,3-diketone moiety of CUR into the isoxazole (ISO) and pyrazole (PYR) derivatives. These derivatives should be much less prone to nucleophilic addition than CUR and benzyl mercaptan addition analyses showed that indeed they do not form isolable conjugated products. When compared with CUR, ISO and PYR exhibited increased cell growth inhibitory and pro-apoptotic effects in liver cancer HA22T/VGH cells as well as in …