Maria D. Vargas

Synthesis of 1-ferrocenyl-2-aryl(heteroaryl)acetylenes and 2-ferrocenylindole derivatives via the Sonogashira–Heck–Cassar reaction

Abstract The Sonogashira–Heck–Cassar reaction of ferrocenylacetylene with aryl- and heteroaryl halides was shown to be a facile and convenient route for the synthesis of 1-ferrocenyl-2-aryl- and 1-ferrocenyl-2-heteroarylacetylenes in high yields. Additionally, annulation reactions of some of the 1-ferrocenylacetylene compounds gave 2-ferrocenyl-2-benzo[ b ]furan and 2-ferrocenylindoles in good yields.

Secondary amines and unexpected 1-aza-anthraquinones from 2-methoxylapachol

A series of 1-aza-anthraquinones were characterized, besides the expected N-alkylamino derivatives, from the substitution reactions of 2-methoxylapachol with primary amines. An investigation of the reaction conditions allowed reasonable selectivity in the products distribution.

The synthesis and reactivity of the heptanuclear dianion [Os7(CO)20]2− including the synthesis and structural characterizations of the compounds [Os7(CO)20(AuPEt)32] and [Os8(CO)20(η6-C6H6]

Reduction of the heptaosmium cluster [Os7(CO)21] With [Et4N][NH4) gives the cluster dianion [Os7(CO)20]2−,1, in high yield. The reaction of the dianion with [AuPR3Cl] (R=Et or Ph) in the presence of TlPF6 forms [Os7((CO)20(AuPR3)2] [R=Et (2a);R = Ph(2b)] in 80% yield, while the corresponding reaction with (Os(C6H6)(CH3CN)3]2+ gives [Os8(CO)20 (η6-C6H6)] (3) in reasonable yield (ca. 30%). The dianion,1, and the clusters2 and3 have been fully characterized by bout spectroscopic and crystallographic methods. The crystal structure of the [Ph4P]+ salt of1 shows that the metals in the anion adopt a capped octahedral geometry, with all twenty carbonyl ligands in terminal sites. The metal core geometry in2a is best described as a tricapped octahedron, and is based on the structure of the dianion1 with two adjacent octahedral faces capped by the Au atoms of the two AuPEt3 groups. In a similar fashion, the geometry of3 is related to that of1 with the addition of an Os(C6H6) unit capped to a triangular face, to give a bicapped octahedral framework.

Synthesis and X-ray analysis of the tetrahydrido-dianion [H4Os10(CO)24]2–, the first non-carbido decaosmium cluster

The non-carbido decaosmium cluster dianion [H4Os10(CO)24]2–(1) has been prepared in low yield by heating several trinuclear osmium clusters in isobutyl alcohol; X-ray analysis of the [(Ph3P)2N]+ salt shows that the tetrahydrido-dianion (1) is very similar in structure to the carbido-dianion [Os10C(CO)24]2–(2) indicating that the four hydrido-ligands in (1) may possibly be interstitial in the solid state.

Synthesis and Structural Characterization of [Ir4(mu-CO)(CO)7{mu4-eta3-Ph2PC(H)C(Ph)PCBu t}(mu-PPh2)]: Alkyne-Phosphaalkyne Coupling and Formation of a Novel 2-phosphabutadienylphosphine Ligand

A reacao de [Ir4(m-H)(CO)9(Ph2PCoCPh)(m-PPh2)] 1 com PoCBut em CH2Cl2 a 35 °C por 4 h leva a formacao do composto inedito [Ir4(m-CO)(CO)7{m4-h3-Ph2PC(H)C(Ph)PCBut}(m-PPh2)] 2, que contem a cadeia 2-fosfabutadienilfosfina. O composto 2 forma-se tambem quando [Ir4(CO)10(Ph2PCoCPh)(PPh2H)] 3 e aquecido na presenca de PoCBut, em thf, a 40 °C, por 48 h. Essas duas reacoes tambem produzem pequenas quantidades de [Ir4(m-CO)(CO)7(m3-h2-HCCPh)(m-PPh2)2] 4, porque as velocidades das transformacoes de 1 e de 3 em 4 e das reacoes desses compostos com PoCBut sao semelhantes. O composto 2 foi caracterizado por dados analiticos e espectroscopicos, espectrometria de massas usando fonte de FAB e experimentos de RMN de 1H, 31P, 13C, 2D 31P-1H HETCOR, diferenca de nOe e DEPT que levaram a sua formulacao e estabeleceram que havia ocorrido o acoplamento entre o ligante Ph2PCoCPh e o PoCBut e a migracao do hidreto para o Ca do Ph2PCoCPh. Entretanto, esses dados nao permitiram decidir se a clivagem da ligacao P-Csp do Ph2PCoCPh havia ocorrido e nem definir o modo de interacao da cadeia organofosforada. A estrutura molecular do composto 2, determinada por uma analise de difracao de raios-X, mostrou que o cluster exibe um arranjo metalico na forma de uma borboleta e que a cadeia organofosforada, corretamente formulada por dados espectroscopicos, interage com o poliedro metalico atraves de quatro ligacoes s.

Azepines from the intramolecular Prins cyclization of an aminoderivative of lapachol

Abstract Intramolecular Prins reaction of the 2-(2,2-dimethoxyethylamino)-3-(3-methyl-2-butenyl)-1,4-dihydro-1,4-naphthalene-6,11-dione, an amino derivative of lapachol, under hydrolytic conditions, yielded novel azepines condensed with the naphthoquinone nucleus of lapachol.

Synthesis and structural characterization of the first transition metal cluster containing a PPh2AuPPh3 ligand, Ir4(CO)8(μ-CO)3(PPh2AuPPh3), and its conversion into Ir4(CO)9(μ-CO)(μ-PPh2)(μ-AuPPh3)

Abstract Deprotonation of Ir 4 (CO) 11 PPh 2 H ( 1 ) in the presence of [AuPPh 3 ][PF 6 ] yields the novel species Ir 4 (CO) 11 (PPh 2 AuPPh 3 ) ( 2 ), which possesses a tetrahedral framework bearing a terminally bound PPh 2 AuPPh 3 ligand. When heated in toluene, 2 is converted into the phosphido species Ir 4 (CO) 10 (μ-PPh 2 )(μ-AuPPh 3 ).

Synthesis and characterisation of derivatives of [HIr4(CO)10(μ-PPh2)] with mono and diphosphines; X-ray molecular structures of [HIr4(CO)8(PPh3)2(μ-PPh2)] and [HIr4(CO)8{Ph2P(CH2)nPPh2}(μ-PPh2)] (n=1 and 4)

The reactions of the cluster compound [HIr 4 (CO) 10 (μ-PPh 2 )] ( 1 ) with a series of phosphines, PMe 3 and PPh 3 , and diphosphines, Ph 2 P(CH 2 ) n PPh 2 ( n =1, dppm, n =2, dppe and n =4, dppb) and cis -PPh 2 CHue605CHPPh 2 (dppen), have been investigated. Reaction of 1 with PMe 3 yielded the mono and di-substituted derivatives [HIr 4 (CO) 10− n (PMe 3 ) n (μ-PPh 2 )] ( n =1, 2 and n =2, 3 ). 1 H and 31 P-NMR spectroscopy monitoring revealed that the two kinetic isomers 2b and 2c undergo conversion to the thermodynamic isomer 2a through a process, which apparently involves intra-molecular migration of the PMe 3 ligand. In contrast, analogous kinetic isomers were not detected during the synthesis of the PPh 3 derivative [HIr 4 (CO) 9 (PPh 3 )(μ-PPh 2 )] ( 4 ). According to 1 H and 31 P-NMR data, compounds [HIr 4 (CO) 8 (L) 2 (μ-PPh 2 )] (L=PMe 3 3 and PPh 3 5 ) exist in solution in three isomeric forms 3a – 3c and 5a – 5c , respectively, at −60xa0°C. Compound 1 also reacts with diphosphines to give CO substitution products, whose composition depends on the size of the methylene chain. Whilst reaction with dppm and dppen yields only the bi-substituted species [HIr 4 (CO) 8 (dppm)(μ-PPh 2 )] ( 6 ) and [HIr 4 (CO) 8 (dppen)(μ-PPh 2 )] ( 7 ), respectively, with dppb, both the dimeric compound [{HIr 4 (CO) 9 (μ-PPh 2 )} 2 (dppb)] ( 8a ) and the monomeric species [HIr 4 (CO) 8 (dppb)(μ-PPh 2 )] ( 8b ) are formed, and with dppe, only the dimeric compound [{HIr 4 (CO) 9 (μ-PPh 2 )} 2 (dppe)] ( 9 ) is obtained. The dppm derivative exists in solution in the form of two inter-converting isomers 6a and 6b that differ with respect to the mode of coordination of the dppm and CO ligands. Isomerisation of 6a – 6b is proposed to involve intra-molecular migration of dppm and carbonyl ligands. Structures were proposed for all compounds, on the basis of 1 H and 31 P[ 1 H]-NMR studies and of correlations previously established for the phosphine and diphosphine derivatives of [Ir 4 (CO) 12 ]; the molecular structures of compounds 5c , 6a and 8b were established by X-ray diffraction studies which confirmed the structures proposed based on spectroscopic data.

Synthetic Lapachol Derivatives Relax Guinea-Pig Ileum by Blockade of the Voltage-Gated Calcium Channels

The present study was designed to further evaluate a possible spasmolytic activity of synthetic lapachol derivatives, norlapachol, α-norlapachone, β-norlapachone and hydro-hydroxy- norlapachol (HH-norlapachol), on guinea-pig ileum. In guinea-pig ileum, except for norlapachol, all naphthoquinones inhibited the phasic contractions induced by carbachol or histamine. Even when the ileum was pre-contracted with KCl, carbachol or histamine, all naphthoquinones induced relaxation, suggesting that these naphthoquinones could be acting on the voltage-gated calcium channels (CaV). As the tonic component this contraction is maintained mainly by the opening of the CaV, we hypothesized that these naphthoquinones might be acting on these channels. This hypothesis was confirmed by the observation that norlapachol (pD’2 = 4.99), α-norlapachone (pD’2 = 4.49), β-norlapachone (pD’2 = 6.33), and HH-norlapachol (pD’2 = 4.53) antagonized the contractions induced by CaCl2 in depolarizing medium nominally without Ca2+. As β-norlapachone was the most potent we decided to continue the study of its action mechanism. The fact that this naphthoquinone has inhibited the tonic contractions induced by S-(-)-Bay K8644 [EC50 = (1.6 ± 0.30) · 10-5 M] suggests that the Ca2+ channel involved belongs to the type L (CaV1.2). In addition, in the functional level, the spasmolytic effect of β-norlapachone does not involve participation of free radicals, since its curve of relaxation was unchanged in the presence of glutathione, an antioxidant agent.

Oxidative Addition Reactions of I2 with [HIr4(CO)10-n(PPh3 )n(μ-PPh2)] (n = 1 and 2) and Crystal and Molecular Structure of [HIr4(μ-I)2(CO)7 (PPh3)(μ-PPh2)]

As reacoes dos compostos [HIr4(CO)10-n(PPh3 )n(μ-PPh2)] [n = 0, (1); 1, (2) e 2, (3)] com I2 foram investigadas. O composto 1 nao reage, porem, a substituicao de ligante(s) CO por PPh3 leva a ativacao do cluster. De fato, ambos os compostos 2 e 3 reagem com I2 em condicoes brandas com a formacao de [HIr4(μ-I)2(CO)7(PPh3)(μ-PPh 2)] (4), como resultado da adicao oxidativa de I2 e dissociacao de dois ligantes CO ou de um CO e uma PPh3, respectivamente. A estrutura molecular de 4, determinada por um estudo de difracao de raios X, exibe um arranjo metalico na forma de uma borboleta, cujas asas se encontram ligadas pelo ligante em ponte μ-PPh2; os atomos que formam o corpo da borboleta se encontram ligados a um ligante μ-H, e cada uma das duas asas contem um ligante iodo ligado em ponte; todos os atomos metalicos contem dois ligantes CO terminais, excecao feita de um dos atomos do corpo da borboleta que contem um ligante CO e um PPh3. O cluster exibe a menor distância media de ligacao Irx96Ir observada ate hoje em derivados do composto 1, o que esta de acordo com o fato de o estado de oxidacao medio dos centros metalicos (+1) ser relativamente alto para clusters metalicos carbonilicos.