27686-42-6Relevant academic research and scientific papers
Selenenate Anions (PhSeO?) as Organocatalyst: Synthesis of trans-Stilbenes and a PPV Derivative
Zheng, Zhipeng,Trofymchuk, Oleksandra S.,Kurogi, Takashi,Varela, Elena,Mindiola, Daniel J.,Walsh, Patrick J.
, p. 659 - 666 (2020)
The selenenate anion (RSeO?) is introduced as an active organocatalyst for the dehydrohalogen coupling of benzyl halides to form trans-stilbenes. It is shown that RSeO? is a more reactive catalyst than the previously reported sulfur analogues (sulfenate anion, RSO?) and selenolate anions (RSe?) in the aforementioned reaction. This catalytic system was also applied to the benzylic-chloromethyl-coupling polymerization (BCCP) of a bis-chloromethyl arene to form ppv (poly(p-phenylene vinylene))-type polymers with high yields, Mn (average molecular weight) up to 13,000 and ? (dispersity) of 1.15. (Figure presented.).
Unequivocal experimental evidence for a unified lithium salt-free wittig reaction mechanism for all phosphonium ylide types: Reactions with β-heteroatom-substituted aldehydes are consistently selective for cis-oxaphosphetane-derived products
Byrne, Peter A.,Gilheany, Declan G.
, p. 9225 - 9239 (2012/07/14)
The true course of the lithium salt-free Wittig reaction has long been a contentious issue in organic chemistry. Herein we report an experimental effect that is common to the Wittig reactions of all of the three major phosphonium ylide classes (non-stabilized, semi-stabilized, and stabilized): there is consistently increased selectivity for cis-oxaphosphetane and its derived products (Z-alkene and erythro-β-hydroxyphosphonium salt) in reactions involving aldehydes bearing heteroatom substituents in the β-position. The effect operates with both benzaldehydes and aliphatic aldehydes and is shown not to operate in the absence of the heteroatom substituent on the aldehyde. The discovery of an effect that is common to reactions of all ylide types strongly argues for the operation of a common mechanism in all Li salt-free Wittig reactions. In addition, the results are shown to be most easily explained by the [2+2] cycloaddition mechanism proposed by Vedejs and co-workers as supplemented by Aggarwal, Harvey, and co-workers, thus providing strong confirmatory evidence in support of that mechanism. Notably, a cooperative effect of ortho-substituents in the case of semi-stabilized ylides is confirmed and is accommodated by the cycloaddition mechanism. The effect is also shown to operate in reactions of triphenylphosphine-derived ylides and has previously been observed for reactions under aqueous conditions, thus for the first time providing evidence that kinetic control is in operation in both of these cases.
Catalytic enantioselective allyl- and crotylboration of aldehydes using chiral diol·SnCl4 complexes. Optimization, substrate scope and mechanistic investigations
Rauniyar, Vivek,Zhai, Huimin,Hall, Dennis G.
supporting information; experimental part, p. 8481 - 8490 (2009/02/02)
We report a novel class of C2-symmetric chiral diols derived from the hydrobenzoin skeleton. The combination of these diols with SnCl 4 under Yamamoto's concept of Lewis acid assisted Bronsted acidity (LBA catalysis) leads to high levels of asymmetric induction in the allylboration of aldehydes by commercially available allylboronic acid pinacol ester 1a. The corresponding homoallylic alcohol products of synthetically useful aliphatic aldehydes are obtained in excellent yields with up to 98:2 er. This combined acid manifold is also efficient in catalyzing the diastereo- and enantioselective crotylboration of aldehydes, thus providing the propionate units in >95:5 dr and up to 98:2 er. The X-ray crystal structure of the optimal diol·SnCl4 complex, Vivol (4m)·SnCl 4, unambiguously shows the Bronsted acidic character of this LBA catalyst and its highly dissymmetrical environment. Further controls have ruled out a possible boron transesterification mechanism with the chiral diol and point to LBA catalyst-derived activation of the pinacol allylic boronates 1. Due to slow dissociation of the diol·SnCl4 complex, a small excess of diol is required in order to suppress a competing racemic cycle catalyzed by free SnCl4.
Short and efficient synthesis of coronene derivatives via ruthenium-catalyzed benzannulation protocol
Shen, Hung-Chin,Tang, Jhih-Meng,Chang, Hsu-Kai,Yang, Chia-Wei,Liu, Rai-Shung
, p. 10113 - 10116 (2007/10/03)
TpRuPPh3(CH3CN)2PF6 (3 mol %) was very active in catalytic benzannulation of 1-phenyl-2-ethynylbenzenes in dichloroethane (60 °C, 36 h) to afford phenanthrene in 95% yield. This method is applicable to the synthesis of various polycyclic aromatic hydrocarbons via two- and four-fold benzannulations, including various substituted coronene derivatives (53-86% yields) using this catalyst at a moderate loading (10 mol %).
Synthesis of succinimido[3,4-b]indane and 1,2,3,4,5,6-hexahydro-1,5-methano-3-benzazocine-2,4-dione by sequential alkylation and intramolecular arylation of enolates derived from N,N,N'N'-tetramethylbutanediamides and N,N,N'N'-tetramethylpentanediamides
Dandekar, Sushama A.,Greenwood, Stacey N.,Greenwood, Thomas D.,Mabic, Stephane,Merola, Joseph S.,Tanko, James M.,Wolfe, James F.
, p. 1543 - 1553 (2007/10/03)
The tricyclic title compounds, 4 and 5, were synthesized by initial alkylation of the lithium monoenolates of N,N,N',N'-tetramethylbutanediamide (6) and N,N,N',N'-tetramethylpentanediamide (19) with 2-iodobenzyl chloride in liquid NH3 at -60°C to afford 2-(2-iodobenzyl)-N,N,N',N'-tetramethylbutanediamide (9) and 2-(2-iodobenzyl)-N,N,N',N'-tetramethylpentanediamide (20) in yields of 88 and 87%, respectively. Treatment of 9 with KNH2 in liquid NH3 resulted in formation and intramolecular arylation of the less-substituted α-enolate to produce trans-1,2-bis(N,N-dimethylcarboxamido)indane (10a) in 60% yield. Selective hydrolysis of 10a with aqueous Na2O2 gave trans-1-(N,N-dimethylcarboxamido)indane-2-carboxylic acid (17), which was then converted to bridged succinimide 4 by transformation to trans-1-(N,N-dimethylcarboxamido)indane-2-carboxamide (10c) followed by cyclization of this mixed primary/tertiary amide by means of NaH in refluxing THF. Treatment of 20 with KNH2 in liquid NH3 led to intramolecular arylation and accompanying ammonolysis to afford trans-1-(N,N-dimethylcarboxamido)-1,2,3,4-tetrahydronaphthalene-3-carboxamide (21b). Conversion of 21b to 5 was similarly effected by means of NaH. Experiments designed to test the mechanistic aspects of the intramolecular arylations provided evidence for competing aryne and SET pathways.
Intramolecular biaryl coupling: asymmetric synthesis of the chiral B-ring unit of pradimicinone
Kelly,Li,Bhushan
, p. 161 - 164 (2007/10/02)
The combination of palladium-catalyzed intramolecular biaryl coupling with enantioselective dihydroxylation of achiral stilbenes provides an efficient, two-step route to the chiral 9,10-dihydrophenanthrenediol unit of the pradimicins and benanomicins.
Chemistry of 8-Substituted 1-Naphtylmethylenes and 2-Substituted Benzylidenes. A simple Entry to 1H-Cyclobutanaphthalenes
Bailey, R. J.,Card, P. J.,Shechter, H.
, p. 6096 - 6103 (2007/10/02)
Study has been made of neighobing heteroatom interaction in thermolysis and photolysis of proximally substituted aryldiazomethanes.Thus, (8-bromo-1-naphthyl)diazomethane (1c) isomerize at 132 deg C to 9-bromo- (18a), 9-iodo- (18b), and 6,9-dichloro-3H-benzindazoles (18c).Indazoles 18a and 18b are reduced by lithium aluminum hydride to 3H-benzindazole (21), identical with that from decomposition of N-(1-methyl-2-naphthyl)-N-nitrosoacetamide (19). 1-Naphthyldiazomethane (1e) does not isomerize however to 21; in benzene at -78 deg c, 1e converts to trans-bis(1-naphthyl)ethylene (22b), 1-naphthalzine (26), and 7-(1-naphthyl)cycloheptatriene (24) wich rearranges to 1-(1-naphthyl)cycloheptatriene (25) whean heated.Irradiation of 1a in ethyl ether results in trans-bis(8-bromo-1-naphthyl)ethylene (22c) and 1-bromo-1Hcyclobutanaphthalene (4a), the first aryne bridged in its peri positions by a single carbon atom moiety.Aqueous silver nitrate converts 4a tp 1H-cyclobutanaphthyl nitrate (4b) and 1-naphthaldehyde (28), presumably by ring opening of 1-hydroxy-1H-cyclobutanaphhtalene (27).Reaction of 4a with magnesium and hydrolysis of the resulting Grignard reagent yield 1H-cyclobutanaphthalene (4d), a hydrocarbon acid wich udergoes deuterium exchange at C-1 considerably slower than to acenaphthene (29) and diphenylmethane (30).Thermolysis and photolysis of diazomethane (1d) to give 2-methyl-2H-naphthothiophene (33) are of note in that methylthio participation in 8-(methylthio)-1-naphthylidene (2d) and thia-Stevens rearrangement appear to be involved. (o-Iodophenyl)diazomethane (5a) thermolyzes to trans-bis(o-iodophenyl)ethylene and o-iodobenzalazine (36); products of reaction of the iodine moiety with the carbenic center in o-iodobenzylidene (6a) were not found.Thermolysis however of (o-(methylthio)phenyl)diazpmethane (5b) results in inrtamolecular C-H insertion to yield 4,5-dihydrothiophene (37) along with trans-bisethylene (38) and o-(methylthio)benzalazine(39).Intermolecular carbenic interception does occur in photolysis of 5b iin that 2-(2-ethoxy-1-propyl)thioanisole (40) is formed along with 398 and 39.The mechanisms of the various participation processes in the above substituted 1-naphthylidenes are discussed.
