Xi:Irritant;
2216-51-5Relevant articles and documents
Acceleration of acid-catalyzed hydrolysis in a biphasic system by sodium tetracyanocyclopentadienides
Sakai, Takeo,Bito, Mariko,Itakura, Makoto,Sato, Honami,Mori, Yuji
, p. 930 - 934 (2016)
The hydrolysis of tert-butyldimethylsilyl L-menthyl ether (3) in a CH2Cl2-1 M HCl biphasic solvent system was accelerated by the addition of sodium tetracyanocyclopentadienides 1. Particularly, the reaction rate was enhanced using sodium salt 1a-c with a lipophilic substituent on the cyclopentadienide ring. From the results obtained by a triphasic experiment, hydrolysis proceeds via the formation of hydronium ion 2 in the aqueous phase by ion exchange, followed by the transfer of 2 to the CH2Cl2 phase.
Selective cleavage of allyl ethers
Lee, Jinhwa,Cha, Jin Kun
, p. 3663 - 3666 (1996)
A simple, one-step method for the selective cleavage of allyl ethers to alcohols has been developed by use of Ti(O-i-Pr)4 and a commercially available Grignard reagent.
C2-Symmetric sulfur derivatives of 2,2′,3,3′'-tetramethoxybiphenyl
Delogu, Giovanna,Fabbri, Davide,Dettori, Maria Antonietta,Forni, Alessandra,Casalone, Gianluigi
, p. 1451 - 1458 (2001)
A practical route to prepare dithioether, thiophene and thiophene S-dioxide derivatives of 2,2′,3,3′-tetramethoxy-1,1′-biphenyl 1 is described. Resolution of 6,6′-bis(methylthio)-3,3′-dimethoxy-[1,1′-biphenyl]-2,2′ -diol 15 was achieved and its absolute configuration was assigned by X-ray analysis of the corresponding phosphorothioamidate diastereomer 18.
Synthesis of new mixed (-)-menthylalkyltin dihydrides. stereoselective reduction of chiral and prochiral ketones
Terraza, V. Fabricio,Gerbino, Darío C.,Podestá, Julio C.
, (2021)
This paper reports de synthesis of a series of (-)-menthylalkyltin dihydrides, (-)-MenRSnH2 (R = Me, n-Bu, i-Pr, t-Bu, Neophyl), starting from (-)-menthyltrimethyltin. The new (-)-menthylalkyltin dihydrides 12–16 were used in a study on the stereoselective reduction of chiral (-)-menthone under different reaction conditions. Also the results obtained in the reductions of prochiral acetophenone (27) and 2-acetylnaphthalene (28), with (-)-menthylmethyl- (12) and (-)-menthyli-propyltin (14) dihydrides are informed. Some physical properties as well as full 1H-, 13C-, and 119Sn NMR data of the new organotin compounds are informed.
Intramolecular cyclization of (+)-citronellal using supported 12-tungstophosphoric acid on MCM-41
Braga, Patricia R.S.,Costa, Andréia A.,De Freitas, Elon F.,Rocha, Rafael O.,De MacEdo, Julio L.,Araujo, Antonio S.,Dias, José A.,Dias, Sílvia C.L.
, p. 99 - 105 (2012)
Supported heteropolyacids (HPAs) have been used as catalysts by fine-tuning their heterogenous and Br?nsted acidic properties. In this work, supported H3PW12O40 (HPW) on MCM-41 was prepared (2-40 wt%) and applied in the intramolecular cyclization of (+)-citronellal. The synthesized materials were characterized by 31P MAS NMR, XRD, FTIR, pyridine gaseous adsorption, low temperature nitrogen adsorption and thermal analysis. The impregnation of 20% HPW on the surface of MCM-41 decreased the characteristic crystallographic reflections of the support, suggesting that HPW modifies the long-range order. The results show that the HPW was deposited preferentially inside the mesopores of the support and affected the acid strength of the supported catalyst. FTIR studies of pyridine adsorption confirmed the presence of Br?nsted and hydrogen bonded acid sites. All synthesized materials were active in the cyclization reaction, but the 20%HPW/MCM-41 sample was the most active. This catalyst showed about 96% conversion and 65% selectivity to the most important stereoisomer (-)-isopulegol, under 1 h reaction. This catalyst was reused four times with a fair degree of deactivation. The decreased activity was attributed to the formation of small agglomerates in the channels of MCM-41.
Chromatography-free Pd-catalyzed deprotection of allyl ethers using PS-DEAM as a scavenger of boronic acids and Pd catalyst
Tsukamoto, Hirokazu,Suzuki, Takamichi,Sato, Masanori,Kondo, Yoshinori
, p. 8438 - 8441 (2007)
Polystyrene-bound diethanolamine (PS-DEAM) work-up for a newly developed Pd(PPh3)4-catalyzed cleavage of allylic alkyl ethers using phenylboronic acid can effectively release Pd-free parent alcohols. Furthermore, chromatography-free deallylation can be conducted by using vinylboronic anhydride pyridine complex as an allyl scavenger with a catalytic amount of Pd(OAc)2 and 4-(diphenylphosphino)benzoic acid instead of Pd(PPh3)4 to yield the desired products in high purities and yields after removal of volatile byproducts and the phosphine-derived contaminants by evaporation and sequestration through acid-base interaction with PS-DEAM, respectively.
Reactions of selenothioic acid S-esters with trivalent phosphorus compounds: New synthetic methods for α-phosphoryl alkyl sulfides and alkyl selenides
Murai, Toshiaki,Izumi, Chiyoko,Itoh, Toshihide,Kato, Shinzi
, p. 917 - 924 (2000)
The reaction of selenothioic acid S-esters 1 with trialkyl phosphites proceeds smoothly with the extrusion of selenium atoms to afford α-phosphoryl sulfides 2 in good to high yields. A similar reaction takes place more easily with dimethyl phenylphosphonite and methyl diphenylphosphinite, although the ketene selenothioacetals 3 are also formed as by-products in increased yields. The use of diselenoic acid esters If and 1g gives α-phosphoryl selenides 2m and 2n. The products exhibit characteristic chemical shifts and coupling constants in their 31P NMR spectra. The structure of α-phosphoryl selenide 2n is confirmed by X-ray molecular structure analysis. The reaction with triphenylphosphine leads to oxidative dimerization of ester 1d to give divinyl diselenide 4 in good yield. A catalytic amount of triphenylphosphine is also effective to form divinyl diselenide 4. The reaction may begin with the nucleophilic attack of triphenylphosphine on the carbon atom of the selenocarbonyl group of ester 1d. Details of the reaction pathway leading to α-phosphoryl sulfides 2 are also discussed. The reaction with menthyl diphenylphosphinite 12 has suggested that the reaction may proceed via initial nucleophilic attack of trivalent phosphorus compounds bearing alkoxy groups on the selenium atom of esters 1. The intermediacy of phosphonium ylide 14 has also been supported by the reaction of the ester 1h which gives 1,4-oxathiane 15.
A thermostable variant of Bacillus subtilis esterase: Characterization and application for resolving dl-menthyl acetate
Gong, Yi,Xu, Guo-Chao,Zheng, Gao-Wei,Li, Chun-Xiu,Xu, Jian-He
, p. 1 - 8 (2014)
Bacillus subtilis esterase (BSE) exhibits high activity, extraordinary substrate/product tolerance and excellent enantioselectivity in the production of l-menthol through enantioselective hydrolysis of dl-menthyl acetate. However, rapid inactivation of wild-type BSE at elevated temperatures often hampers its applications. In this work, directed evolution was used to create thermostable mutants of BSE. After screening and recombination of beneficial mutations, BSEV4 was chose for the best mutant. The BSEV4 had half-lives of 462, 248 and 0.34 h at 30, 40 and 50 °C, respectively, which were 5.6, 4.1 and 2.0 folds longer than those of BSEWT. Moreover, BSEV4 showed an increase of 4.5 °C in T5015 and a higher temperature optimum compared with the wild-type enzyme. In the kinetic resolution of dl-menthyl acetate at 1.0 M substrate loading, BSEV4 displayed improvements in operational stability than BSEWT, leading to a 1.5-fold higher total turnover number at 45 °C. The model structure of BSEV4 with four mutations, built with a highly homologous p-nitrobenzyl esterase (PDB ID: 1QE3) as the template, revealed that the newly formed hydrogen bonds and ionic bonds were beneficial for enhancing the thermostability of BSE.
TRANSFORMATION OF ISOPRENOIDS BY ORCHIDS IN TISSUE CULTURE
Mironowicz, Agnieszka,Kukulczanka, Krystyna,Krasinski, Krzysztof,Siewinski, Antoni
, p. 1959 - 1960 (1987)
Key Word Index - Epidendrum ochraceum; Cymbidium 'Saint Pierre'; Dendrobium phalaenopsis; Orchidaceae; orchids; tissue culture; biotransformations; testosterone; androsterolone; menthyl acetate. Tissue cultures of Epidendrum ochraceum, Cymbidium 'Saint Pierre' and Dendrobium phalaenopsis were found to transform some isoprenoids.The transformation of the oxygen functions at C-17 in androstane derivatives and the hydrolysis of (+/-)-menthyl acetate were investigated in some detail.The degree of hydrolysis of the latter was about 75-85 percent.
A novel benzoyl-type fluorous protecting group for use in fluorous synthesis
Miura, Tsuyoshi,Satoh, Ai,Goto, Kohtaro,Murakami, Yasuoki,Imai, Nobuyuki,Inazu, Toshiyuki
, p. 3 - 6 (2005)
TfBz-OH, a novel benzoyl-type fluorous protecting reagent, has been easily prepared. It was found that the TfBz (trisfluorous chain-type benzoyl) group can be successfully introduced onto a hydroxyl function, removed in high yield, and recycled after deprotection. The use of the TfBz group makes it possible to synthesize an oligosaccharide by minimal column chromatography purification, because each synthetic intermediate is easily purified simply by fluorous-organic solvent extraction.
