Acidities of arenetricarbonylchromium(0) complexes in tetrahydrofuran

The measurement of acidities of arenetricarbonylchromium(0) complexes in tetrahydrofuran reveals the acid-strengthening effect of complexation to be 6–7 pK units and the pK of benzene to be 41.     

Conjugation of Phenothiazine and Substituted Indoles via Copper-Catalyzed 1,3-Dipolar Cycloaddition

Russian Journal of General Chemistry - Copper-catalyzed alkyne-azide 1,3-dipolar cycloaddition of substituted N-azidoalkylindoles and N-propargylphenothiazine led to the formation of conjugates of...     

Enantiopure eta4-(1-sulfinyldiene)iron(0) tricarbonyl complexes as templates for carbocycle construction via ring-closing metathesis

[reaction: see text] Enantiomerically pure 1-(1Z,3E)-sulfinyl iron(0) dienols have been elaborated to bis-olefins capable of undergoing ring-closing metathesis chemistry. Using Grubbs' ruthenium carbene catalyst, a six-membered carbocycle (with one chiral center) and seven-, eight-, and nine-membered carbocycles (with two chiral centers) have been prepared. Novel transformations include the LiClO4-promoted allylation of an alkylidene malonate and a reductive sulfur-carbon bond cleavage to convert a vinyl sulfoxide into an alkene with SmI2.     

An experimental study of various arenetricarbonylchromium complexes

For a series of arenetricarbonylchromium complexes ZCr(CO)₃, analysis of the electric dipole moments in benzene and carbonyl stretching frequencies in cyclohexane suggest the following: for unsubstituted ZCr(CO)₃, with Z = diphenyl, fluorene and cis-stilbene, the π-basicity to be considered is that of the ring directly united to the tricarbonylchromium group, and not that of the arene as a whole. In general, the substituent effect in p-substituted diphenyltricarbonylchromium complexes (Z = 4-methyl-, 4-amino- and 4,4′-dimethyldiphenyl), in which the tricarbonylchromium group is bonded to the substituted phenyl ring, is markedly weaker than that in the corresponding benzenetricarbonylchromium complexes. In 4-fluorodiphenyltricarbonylchromium, the tricarbonylchromium group is attached to the unsubstituted phenyl ring. 4-Aminodiphenyltricarbonylchromium exists in two distinct forms: one with the nitrogen lone pair away from, and the other close to, the metal atom. Diphenylmethanetricarbonylchromium (and its 4,4′-diamino derivative), indanetricarbonyl- and 4,4′-difluorodiphenyltricarbonylchromium have also been examined.     

Synthesis of Substituted (2-Aminophenyl)-3-(and-4-)Pyridinylmethanones

A one-step procedure for the preparation of substituted (2-aminophenyl)-3-(and -4-)pyridinylmethanones is described.     

New iron complexes from nucleophile addition/carbonylation of η4-(1,3-diene)tricarbonyliron(0) complexes

A series of novel organoiron complexes has been isolated and studied by ¹H NMR, ¹³C NMR, and IR spectroscopy. Addition of LiC(CH₃)₂CN to (1,3-cyclohexadiene)tricarbonyliron produces an intermediate which is only stable at low temperature and which is assigned the homoallyl—Fe(CO)₃ anion structure. The intermediate rearranges on warming into a stable complex, for which full spectral data support the structure as an allyl—Fe(CO)₃ anionic species. Interception of the first formed intermediate with CO gives an acylferrate complex with an olefin unit still bound to iron, and methylation then occurs at oxygen to produce an unusual internally-bound (alkene)(methoxyalkylidene)tricarbonyliron species.     

Asymmetric deprotonation—substitution of arenetricarbonylchromium(0) complexes: substituent controlled lithiation with the butyllithium–sparteine system

Attempted enantioselective deprotonation of fluorobenzenetricarbonylchromium(0) with ca. 1 equivalent of butyllithium/(−)-sparteine in ether–hexane at −78°C followed by a chlorotrimethylsilane quench gave the racemic ortho-substituted product. Analogous enantioselective deprotonation of anisoletricarbonylchromium(0), followed by electrophilic quench, gave the 1-(Rp)-substituted complexes in up to 77% yield with 27% e.e., but with methoxymethoxybenzenetricarbonylchromium(0), (4-triisopropylsilyloxymethyl)methoxymethoxybenzenetricarbonylchromium(0) and (N-t-butoxycarbonylaniline)tricarbonylchromium(0), the 1-(Sp)-products were formed in up to 58% yield with 92% e.e. The results are explained in terms of coordinative and non-coordinative enantioselective lithiation.     

(+)- and (-)-1-0, 4-0-bis(p-chlorobenzyl)threitol as novel resolving agents for optically active anthracyclinone synthesis: an efficient synthesis of optically pure 4-demethoxydaunomycinone

(±)-7-Deoxy-4-demethoxydaunomycinone(±)-$\text{3}$) was cleanly resolved by forming a mixture of the diastereomeric acetals ((?)-$\text{9}$ and (+)-$\text{10}$ or (+)-$\text{9}$ and (?)-$\text{10}$ with the title $\text{vicinal}$-diol((+)- or (?)-$\text{5}$) to give optically pure (R)(?)-$\text{3}$. The method for racemizing the undesired enantiomer((S)(+)-$\text{3}$) was also explored. Optically pure (+)-4-demethoxydauno-mycinone ((+)-$\text{2b}$) was elaborated from (R)(-)-$\text{3}$ according to the reported reaction scheme.     

Substituted dipyridylpyridazine rhodium(III) complexes

3,6-Bis(2-pyridyl)pyridazine derivatives (n-dppn) react with hydrated rhodium(III) chloride and bromide (prepared in situ) to give cis-[Rh(n-dppn)₂Cl₂]PF₆·xH₂O (n = 5, 6, 7, 8) and cis-[Rh(n-dppn)₂Br₂]Br·xH₂O (n = 5, 7) complexes, which have been characterized by elemental analyses, conductivity measurements, i.r., electronic and ¹H- and ¹³C-n.m.r. spectra.     

The synthesis of liquid crystalline lanthanide complexes of Schiff's base ligands: N -(4- n -alkoxysalicylidene)-4'- n -alkylanilines

The reaction of N -(4- n -alkoxysalicylidene)-4'- n -alkylanilines with freshly prepared lanthanide salts leads to mesomorphic terbium and dysprosium complexes exhibiting the smectic A phase.     

Stereoselective synthesis of (-)-4-epiaxinyssamine

The synthetic studies towards axinyssamine, a cytotoxic and coral-lethal compound isolated from the Caribbean sponge Axinyssa ambrosia were performed. The Ritter reaction on the key intermediate with chloroacetonitrile, resulted in the introduction of the amino group at C-4 generating the configuration of this stereocentre opposite to that of the natural product. As a result, the first total synthesis of the unnatural (-)-4-epiaxinyssamine was achieved.     

A method for the synthesis of nickel(0) bis(carbene) complexes

A new method leading to Ni(NHC)2 (NHC = IMes, IPri, SIPr(i), SIBu(t)) complexes in moderate to good yields, involves the reaction of NHC (pre-formed or generated in situ) with Ni(CH3)2(tmed), tmed = N,N'-tetramethylethylenediamine; in one case, the intermediate Ni[I(Me2)Pr(i)]2(CH3)2, I(Me2)Pr(i) = N,N'-diisopropyl-4,5-dimethylimidazol-2-ylidene, has been isolated and structurally characterised.     

Pd(0)‐Catalyzed Dearomative Diarylation of Indoles

We have developed a protocol for a Pd(0)‐catalyzed dearomative syn 1,2‐diarylation of indoles using readily available boroxines (dehydrated boronic acids) as coupling partners. This reaction proceeds efficiently using PtBu₃ as the ligand to divergently access to fused indolines while minimizing the extent of direct Suzuki coupling. The scope of the reaction is remarkably broad and all products are obtained as single diastereomers in moderate to excellent yields. We have also compiled data which parallels the steric and electronic properties of both substrate and boroxine with the propensity to undergo the desired dearomative process over direct Suzuki coupling.     

Substituted imidazole complexes of platinum(IV) halides

Platinum(IV) halides formed complexes of the type PtL₂X₄ [L=1-vinyl imidazole (1,-VIm), 1-methylimidazole (1-MeIm), 1,2-dimethylimidazole (1,2-Me₂Im), 1-vinyl-2-methylimidazole (1-V-2-MeIm), 2-methylimidazole (2-MeIm), 2-ethylimidazole (2-EtIm), 2-isopropylimidazole (2-i-PrIm), and 4-methylimidazole (4-MeIm); X=Cl, Br] in neutral aqueous solution. The 1-n-butylimidazole (1-n-BuIm) ligand yielded only (LH)₂PtX₆ compound in the same medium. The compounds were characterised by elemental analyses, IR, UV-VIS and ¹HNMR spectra.     

4-Functionally Substituted 3-Heterylpyrazoles: XIII. 3-Aryl(heteryl)-4-(4-pyrazolyl)-1,2,3,4-tetrahydropyrimidin-2-ones(thiones)

Cyclocondesation of 3-aryl(heteryl)pyrazole-4-carbaldehydes with ethyl acetoacetate and urea (thiourea) in the presence of FeCl₃ · 6H₂O afforded 3-aryl(heteryl)-4-(4-pyrazolyl)-1,2,3,4-tetrahydropyrimidin-2-ones(thiones).__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 1, 2005, pp. 97–98.Original Russian Text Copyright © 2005 by Bratenko, Chornous, Vovk.     

First examples of oxaphosphirane pentacarbonylchromium(0) and -molybdenum(0) complexes: synthesis, structures and reactions

Synthesis of the first oxaphosphirane chromium(0) and molybdenum(0) complexes of the type [{(R(1)PCH(R(2))-O}M(CO)(5)] (R(1) = C(5)Me(5)) (8a-e, 15a-e) and (R(1) = CH(SiMe(3))(2)) (9a-e, 16a-e) via reaction of dichloro(organo)- (1, 2, 10, 11) and chloro(organo)phosphane complexes (3,4,12) with lithium bases and aldehydes 7a-e is reported. Furthermore, bicyclic 1,3-oxaphospholane complexes 17 and 18 have been obtained via O-protonation of oxaphosphirane complexes 8a and 15a with HCl. All complexes were characterized by NMR, IR spectroscopic, mass spectrometric investigations and, in addition, single-crystal X-ray structures of complexes 8a-e, 9a,c, 15a,b,e, 16a-c, 17, 18 are presented and discussed.     

The Synthesis Of Several N-(Substituted Phenylcarbonylamino)-4-(3-cyclohexenyl)-1,2,3,6-tetrahydropyridines as Potential Anti-Inflam-Matory Agents

Several N-(substituted phenylcarbonylamino)-4-cyclohexenyl-1,2,3,6-tetrahydropyridines 7 were synthesized via sodium borohydride reduction of the corresponding N-(substituted phenylcarbonylimino)-4-cyclohexenylpyridinium ylides 6 in absolute ethanol.     

Enantiospecific total synthesis of (-)-4-thiocyanatoneopupukeanane

Enantiospecific synthesis of the natural enantiomer of the marine sesquiterpene (-)-4-thiocyanatoneopupukeanane (6) is described. The bicyclo[2.2.2]octanecarboxylate 14, obtained from (R)-carvone via Michael-Michael reaction, was transformed into neopupukeananedione 12 by employing rhodium acetate catalyzed intramolecular C-H insertion of the diazo ketones 16 or 19 as the key reaction. Regioselective deoxygenation of the C-2 ketone transformed the dione 12 into neopupukean-4-one 10. Alternately, the keto ester 18 was also transformed into neopupukean-4-one 10 via regioselective deoxygenation of the ketone in 18 followed by intramolecular rhodium carbenoid C-H insertion of the diazo ketone 31. Finally, neopupukean-4-one 10 was transformed into (-)-4-thiocyanatoneopupukeanane 6 via the alcohol 32 and the mesylate 33.     

Facile synthesis of new polyolefinic ruthenium(0) complexes from ruthenium(II) precursors

The new ruthenium(II) complex [(C₈H₁₀)RuCl₂]_n (1) (C₈H₁₀ = 1,3,5-cyclooctatriene; n ⩾ 2) has been obtained from the reaction of RuCl₃·xH₂O with 1,3,5,7-cyclooctatetraene in refluxing ethanol. Reduction of [(C₈H₁₀)RuCl₂]_n and [(C₇H₈)RuCl₂]₂ (2) (C₇H₈ = 1,3,5-cyclooctatriene) by Na/Hg amalgam in the presence of isoprene (C₅H₈) gives the novel ruthenium(O) complexes [(η⁶-C₈H₁₀)Ru(η⁴-C₅H₈)] (3) and [(η⁶-C₇H₈)Ru(η⁴-C₅H₈)] (4). [(η⁶-C₇H₈Ru(η⁴-C₅H₈)] reacts with CO and HBF₄ to give [(η⁶-C₇H₈)Ru(η³-C₅H₉)(CO)][BF₄] (C₅H₉ = trans-1,2-dimethylallyl (5a); 1,1-dimethylallyl (5b)).     

Stereoselective synthesis of 4-(N-mesylamino)-2,3-unsaturated- alpha-O-glycosides via a new glycal-derived vinyl alpha-N-(mesyl)-aziridine

[reaction: see text] N-Mesyl aziridine 7alpha, a new activated vinyl aziridine derived from d-glucal, has been synthesized by cyclization of trans-N,O-dimesylate 6 with t-BuOK in anhydrous benzene. The reaction of 7alpha with alcohols, phenol, and monosaccharides (O-nucleophiles) leads to the corresponding 4-N-(mesylamino)-2,3-unsaturated-O-glycosides and disaccharides through a completely regioselective 1,4-addition process that proceeds with high or complete alpha-stereoselectivity.