- Temperature Controls Guest Uptake and Release from Zn4L4 Tetrahedra
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We report the preparation of triazatruxene-faced tetrahedral cage 1, which exhibits two diastereomeric configurations (T1 and T2) that differ in the handedness of the ligand faces relative to that of the octahedrally coordinated metal centers. At lower temperatures, T1 is favored, whereas T2 predominates at higher temperatures. Host-guest studies show that T1 binds small aliphatic guests, whereas T2 binds larger aromatic molecules, with these changes in binding preference resulting from differences in cavity size and degree of enclosure. Thus, by a change in temperature the cage system can be triggered to eject one bound guest and take up another.
- Zhang, Dawei,Ronson, Tanya K.,Güryel, Songül,Thoburn, John D.,Wales, David J.,Nitschke, Jonathan R.
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supporting information
p. 14534 - 14538
(2019/10/11)
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- [(NHC)CoR2]: pre-catalysts for homogeneous olefin and alkyne hydrogenation
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A novel synthesis for dialkyl cobalt compounds [(tmeda)CoR2] is presented. In these complexes tmeda is readily replaced by an NHC or a bidentate phosphine ligand to form 3- and 4-coordinate compounds, respectively. [(ItBu)Co(CH2SiMe3)2] (ItBu = 1,3-di-tert-butylimidazolin-2-ylidene) serves as an efficient, homogeneous olefin hydrogenation pre-catalyst and allows the preparation of the novel cobalt bis(alkyne) complex [(ItBu)Co(η2-PhCCPh)2].
- Enachi, Andreea,Baabe, Dirk,Zaretzke, Marc-Kevin,Schweyen, Peter,Freytag, Matthias,Raeder, Jan,Walter, Marc D.
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supporting information
p. 13798 - 13801
(2018/12/14)
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- An improved and efficient synthesis of pinene based bipyridyldiols and bipyridine
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An improved and efficient synthesis of pinene based two bipyridyldiols and bipyridine is reported. For the first time, the sealed tube-pressure reaction of pinene based pyridone with phosphoryl chloride produced an excellent yield (95%) of pinene based 2-chloropyridine, which renders synthesizing pinene based bipyridyldiols a highly inexpensive and high yielding process. Moreover, highly effective reaction condition was developed for homocoupling of chloropyridine with Ni(0) that afforded pinene based bipyridine in a high yield (84%). These newly demonstrated sealed tube-pressure chlorination and homocoupling reaction of chloropyridine afford extremely effect route for the synthesis of pinene based bipyridine.
- Boobalan, Ramalingam,Chen, Chinpiao
-
supporting information
p. 1930 - 1934
(2016/04/19)
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- ODORANT COMPOSITION CONTAINING ALLYL ETHERS AS ODORANT PRECURSORS
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The deliberate release of odorants or aroma substances is desirable in many fields of application, and in particular in the field of washing and cleaning agents. Said deliberate release is achieved by using an odorant composition that comprises an odorant precursor, which is an allyl ether of the formula (I), R1R2C═CR3—CR4R5—O—CHR6R7, in which the residues R1, R2, R3, R4, R5, R6 and R7 mutually independently denote H or a hydrocarbon residue that can be acyclic or cyclic, substituted or unsubstituted, branched or unbranched, as well as saturated or unsaturated. Thus, in particular odorants in the form of an alkene having an allylic hydrogen atom, such as α-pinene, can be released in a deliberate manner.
- -
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Paragraph 0123
(2014/02/16)
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- Synthesis of nopol via Prins condensation of β-pinene and paraformaldehyde catalyzed by sulfated zirconia
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The present work describes the novel application of sulfated zirconia (SZ) solid acid catalysts for the synthesis of nopol via Prins condensation of β-pinene and paraformaldehyde. SZ catalysts with different percentages of sulfur loadings have been synthesized and characterized using various physico-chemical techniques like PXRD, FT-IR, surface area analysis and NH 3-TPD studies. The influences of various reaction parameters such as sulfur loading, reaction temperature, molar ratio of reactants, reaction time, solvent effect and reusability of the catalyst have been investigated. SZ catalyst synthesized by impregnation of 2N sulfuric acid solution over Zr(OH)4 was found to be a highly selective catalyst for β-pinene conversion (>99%) with ～99% selectivity to nopol. The catalyst could be reused up to five cycles with minor loss in catalytic activity for β-pinene conversion, while the nopol selectivity remains unaffected.
- Jadhav, Sumit V.,Jinka, Krishna Mohan,Bajaj, Hari C.
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scheme or table
p. 158 - 165
(2011/12/21)
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- Synthesis of silylated alkylboronic acids and esters via hydroboration of allylic and vinylic trimethylsilanes
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Representative allylic trimethylsilanes and isopropenyltrimethylsilane were hydroborated with dichloroborane, and the products were transformed into the corresponding ssor γ-trimethylsilylboronates. Synthesis of 2-trimethylsilylethylboronic acid and its diethyl ester via hydroboration of trimethylvinylsilane with diisopinocampheylborane, followed by liberation of α-pinene is described.
- Cytarska,Kaczanowska,Zaidlewicz
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p. 1587 - 1594
(2008/09/18)
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- Regio- and stereoselective synthesis of the enantiomers of monoterpene-based β-amino acid derivatives
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The regio- and stereospecific addition of chlorosulfonyl isocyanate to cis-δ-pinene enantiomers has furnished monoterpene-fused β-lactams. The observed regioselectivity can be explained by ab initio DFT modeling of transition state structures. In contrast with the less reactive α-pinane-fused β-lactam 4, the resulting β-lactams 5 and 13 containing an amino group connected to a secondary carbon possess similar reactivity to the cycloalkane-fused analogues and can be easily converted to the β-amino acid and its protected derivatives. The base-catalyzed isomerization of the cis-amino ester afforded the corresponding trans-amino ester in moderate yield.
- Szakonyi, Zsolt,Martinek, Tamas A.,Sillanpaeae, Reijo,Fueloep, Ferenc
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p. 2442 - 2447
(2008/03/13)
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- Incorporation of an allene unit into α-pinene via β- elimination
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The two double-bond isomers 3-iodo-2,6,6-trimethylbicyclo[3.1.1]hept-2-ene (6b) and 3-iodo-4,6,6-trimethylbicyclo[3.1.1]hept-2-ene (11) were synthesized by reacting 2,6,6-trimethylbicyclo[3.1.1]heptan-3-one (9) with hydrazine, followed by treatment with I2 in the presence of Et3N. Treatment of 11 with t-BuOK as base in diglyme at 220 resulted in the formation of 9 and 6,6-dimethyl-4-methylidenebicyclo[3.1.1]hept-2-ene (12). For the formation of 9, the cyclic allene 7 is proposed as an intermediate. Treatment of the second isomer, 6b, with t-BuOK at 170 gave rise to the diene 12 and the dimerization product 17. The underlying mechanism of this transformation is discussed. On the basis of density-functional-theory (DFT) calculations on the allene 7 and the alkyne 15, the formation of the latter as the intermediate was excluded. Verlag Helvetica Chimica Acta AG.
- Kilbas, Benan,Azizoglu, Akin,Balci, Metin
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p. 1449 - 1456
(2007/10/03)
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- Molecular addition compounds. 14. Convenient preparations of representative dialkylborane reagents using the new, highly reactive N- ethyl-N-isopropylaniline-borane reagent (BACH-EI(TM))
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Convenient procedures for the preparation of representative dialkylborane reagents, diisopinocampheylborane, [1S]-2-diisocaranylborane, 9-borabicyclo[3,3,1]nonane, dicyclohexylborane and disiamylborane, using the new, highly reactive N-ethyl-N-isopropylaniline-borane reagent (BACH-EI(TM)) in dioxane and tetrahydrofuran are described.
- Brown, Herbert C.,Kanth, Josyula V. B.,Zaidlewicz, Marek
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p. 5991 - 6000
(2007/10/03)
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- Chiral synthesis via organoboranes. 48. Efficient synthesis of trans- fused bicyclic and cyclic ketones and secondary alcohols in high optical purities via asymmetric cyclic hydroboration with isopinocampheylchloroborane etherate
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Highly stereo- and enantioselective annelation has been achieved for the synthesis of trans-fused bicyclic and cyclic ketones via the asymmetric cyclic hydroboration of suitable cyclic dienes, such as 1-allyl-1- cycloalkenes or 1-vinyl-1-cycloalkenes and appropriate acyclic 1,4-dienes, respectively, with enantiomerically pure isopinocampheylchloroborane etherate (IpcBHCl·Et2O). The IpcBHCl· Et2O (an 86-90% equilibrium mixture) was readily synthesized by the reaction of an equivalent amount of hydrochloric acid in ethyl ether (Et2O) with optically pure isopinocampheylborane (IpcBH2). The hydroboration of the terminal double bond of a representative diene with IpcBHCl·Et2O readily provided the corresponding isopinocampheylalkylchloroborane (IpcRBCl). Subsequent hydridation of the IpcRBCl with lithium aluminum hydride (LAH, 0.25 equiv) at -20 or -25 °C generated the intermediate isopinocampheylalkylborane (IpcRBH) almost instantly, which then underwent a rapid stereospecific and enantioselective intramolecular cyclic hydroboration to provide the intermediate cyclic trialkylborane. This trialkylborane, on treatment with an aldehyde, liberated the optically pure auxiliary as α-pinene (readily recovered for recycle) to provide the corresponding cyclic borinate ester. This ester reacted smoothly with α,α-dichloromethyl methyl ether (DCME) in the presence of a hindered base (the DCME reaction) to yield, after oxidation with buffered hydrogen peroxide, the trans-fused bicyclic or cyclic ketone in high enantiomeric excess (ee). In another improved approach, in situ generated IpcBHCl·Et2O, from the reduction of isopinocampheyldichloroborane (IpcBCl2) with trimethylsilane (Me3SiH), in the presence of representative dienes in Et2O provided considerably improved optical yields of the bicyclic and cyclic ketones. The trialkylboranes obtained from suitable acyclic dienes can be easily protonolyzed to provide the secondary alcohols in high ee.
- Dhokte, Ulhas P.,Pathare, Pradip M.,Mahindroo, Verinder K.,Brown, Herbert C.
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p. 8276 - 8283
(2007/10/03)
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- New Chiral Dichlorophosphines and Their Use in the Synthesis of Phosphetane Oxides and Phosphinic Chlorides
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Myrtanyl-, bornyl- and isopinocampheyldichlorophosphines have been prepared from the corresponding alkyl chlorides via diastereospecific reactions of the Grignard reagents with PCl3 or (Et2N)2-PCl. Two applications of these compounds to synthetic asymmetric organophosphorus chemistry have been examined: their reactions with 2,3,3-trimethylbutene and AlCl3 afford either P-chiral phosphetane oxides or, in the presence of gaseous HCl, P-chiral phosphinic chlorides with moderate to high diastereoselectivity.
- Marinetti, Angela,Buzin, Francois-Xavier,Ricard, Louis
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p. 297 - 301
(2007/10/03)
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- Medium- and sensitizer-dependent radical cation reactions: Deprotonation in fluid solution and solid matrices
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Radical cations generated by photo-induced electron transfer in solution or by chemical oxidation in the channels of a redox-active zeolite (NaZSM-5) may be deprotonated, giving rise to neutral radicals. In solution, the geminate radical anion or an added nucleophile (methanol) may serve as the proton acceptor. Deprotonations in solution are not efficient; the corresponding products may be suppressed by several competing intra- or bi-molecular reactions. Although methanol serves as the base deprotonating at least one radical cation, it often is more efficient as a nucleophile, thereby depressing deprotonation. Deprotonations in the zeolite are more effective, presumably, because competing reactions with outside reagents are precluded. Occasionally, NaZSM-5 zeolites promote complex reaction sequences, such as the conversion of p-propylanisole to the radical cation of anethole or the deprotonation-ring opening of 1,2-diphenylcyclopropane radical cation to exo,exo-diphenylallyl radical. Acta Chemica Scandinavica 1997.
- Roth, Heinz D.,Weng, Hengxin,Zhou, Dahui,Lakkaraju, Prasad S.
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p. 626 - 635
(2007/10/03)
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- Chiral Synthesis via Organoboranes. 35. Simple Procedures for the Efficient Recycling of the Terpenyl Chiral Auxiliaries and Convenient Isolation of the Homoallylic Alcohols in Asymmetric Allyl- and Crotylboration of Aldehydes
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Asymmetric allyl- and crotylboration of aldehydes, RCHO, with terpenyl-based allyl- and crotylborane reagents Ter2*BAll (1), Ter2*BCrtZ (2), and Ter2*BCrtE (3, Ter* = Ipc, 4-Icr and 2-Icr; All = allyl and Crt = crotyl), afford Ter2*BOCH*(R)C*(1R)(2R)CH=CH2 intermediates 4.In these reactions, the isolation of homoallylic alcohols, HOCH*(R)C*(1R)(2R)CH=CH2 (5), can be accomplished via oxidation of 4 with alkaline hydrogen peroxide.Unfortunately, oxidative workup destroys the chiral auxiliary and produces a large amount of nonrecyclable byproduct, terpenol (Ter*OH).Further, isolation of the pure homoallylic alcohol by distillation can be difficult if it boils in the range of the abundant byproduct.Therefore, in order to recycle the chiral auxiliaries and isolate the product homoallylic alcohols in an efficient manner, we have developed the following procedures: (1) elimination workup, in which enantiomerically pure α-pinene and Δ2- and Δ3-carenes are liberated from terpenylborinates 4 by treatment with isobutyraldehyde and 1 mol percent BF3*OEt2; (2) ethanolamine workup involving treatment of 4 with ethanolamine (EA) to achieve the precipitation of the ethanolamine adducts (EA-BTer2*, Ter* = Ipc and 2-Icr, 11 and 12) from which the Ter2*BOMe can be easily regenerated; and (3) 8-hydroxyquinoline workup, involving treatment of 4 with 8-hydroxyquinoline (8-HQ) to precipitate the 8-HQ adducts (8-HQ-BTer2*, Ter* = Ipc, 4-Icr and 2-Icr, 13-15), from which the various Ter2*BOMe intermediates can be conveniently liberated.It is hoped that these procedures will significantly enhance the scope of asymmetric allyl-/crotylboration of aldehydes with Ter2*BAll (1), Ter2*BCrtZ (2), and Ter2*BCrtE (3) and serve as excellent alternatives for any catalytic versions yet to be discovered.
- Brown, Herbert C.,Racherla, Uday S.,Liao, Y.,Khanna, Vijay V.
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p. 6608 - 6614
(2007/10/02)
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- Chiral Synthesis via Organoboranes. 14. Selective Reductions. 41. Diisopinocampheylchloroborane, an Exceptionally Efficient Chiral Reducing Agent
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Diisopinocampheylchloroborane, readily prepared in both enantiomers in high chemical and optical purities (99percent ee) via hydroboration followed by treatment with dry hydrogen chloride in ethyl ether, reduces prochiral ketones at convenient rates in tetrahydrofuran at -25 deg C.Reduction of simple dialkyl ketones, 2-butanone, 2-octanone, and 3-methyl-2-butanone, yields the corresponding alcohols with 4percent, 7percent, and 32percent optical induction.On the other hand, aralkyl ketones are reduced with very high asymmetric induction.Thus, acetophenone, propiophenone, butyrophenone, and decanophenone are reduced with 98percent, 98percent, and 97percent ee, respectively.Branching of the alkyl chain diminishes the induction.Isobutyrophenone and pivalophenone are reduced in 78percent and 79 ee, respectively.Functional groups in the aromatic ring are not affected by the reagent and do not appear to influence significatly the optical yield realized.Thus, 2',5'-dimethoxypropiophenone is reduced in 96percent ee. 1-Indanone and α-tetralone are reduced in 98percent and 87percent ee, respectively. 2'-Acetonaphthone is reduced in 98percent ee.Heteroaryl alkyl ketones are also reduced with excellent optical induction.Thus, 3-acetylpyridine and 2-acetylthiophene are reduced in 92percent and 91percent ee, respectively.The reagent reduces α-tertiary aliphatic ketones under neat condition at room temperature with very high optical induction. 3,3-Dimethyl-2-butanone, ethyl 2,2-dimethylacetoacetate, 2,2-dimethylcyclopentanone, 2,2-dimethylcyclohexanone, and spirononan-1-one are reduced to the corresponding alcohols in 95percent, 84percent, 98percent, 91, and 95percent ee, respectively.Some α,β-unsaturated ketones are reduced with lesser optical induction, such as 4-phenyl-3-butyn-2-one and 2-cyclohexenone, which are reduced to the alcohols in 21 and 36percent ee respectively.On the other hand, trans-4-phenyl-3-buten-2-one is reduced to the alcohol.Certain α-keto esters are reduced in 50-70percent ee.The mechanism of the reduction is postulated to be via a six-membered cyclic "boatlike" transition state.X-ray crystal structure data for the reagent are presented.
- Brown, Herbert C.,Chandrasekharan, J.,Ramachandran, P. V.
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p. 1539 - 1546
(2007/10/02)
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- A TRICYCLIC TERPENE HYDROCARBON - CYCLOPINENE
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The reduction of the tosylate of filipendulol (2,7,7-trimethylbicyclohept-2-en-6-ol) with lithium tetrahydroaluminate in ether has given a hydrocarbon (I), C10H16 (bp 66.5 deg C/50 mm, n20D 1.4565, d2020 0.8599, 19D -104.5 deg.NMR: 0.69 ppm (CH3); 0.95 ppm, (CH3); 1.17 ppm (CH3); no signals of olefinic protons.IR: 3054 cm-1 (three-membered ring with gem-protons); 1363 and 1387 cm-1 (gem-CH3), absorption bands of multiple bonds absent.Heating (70 deg C) (I) with a sulfonated cation-exchange resin in hexane gave α-pinene.The hydrogenation of (I) over PtO2 in acetic acid gave pinane.The most probable structure of (I) is 2,7,7-trimethyltricyclo2,4>heptane.The substance has been called cyclopinene.
- Dembitskii, A. D.,Yurina, R. A.,Goryaev, M. I.
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p. 671 - 673
(2007/10/02)
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- Ring Opening of Oxiranes by Trimethylsilyl Trifluoromethanesulfonate
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Trimethylsilyl trifluoromethanesulfonate promotes ring opening reactions of oxirane derivatives.The reaction course is highly affected by the structures and substitution pattern of the substrates.Tetra-, tri, and 2,2-disubstituted oxiranes and simple cycloalkene oxides are converted to the corresponding allylic alcohol trimethylsilyl ethers.The overall transformation is interpreted in terms of trans addition of the silyl trifluoromethanesulfonate to the oxirane ring followed by base-promoted anti elimination of a trifluoromethanesulfonic acid element. 2,3-dialkyl- or monoalkyloxiranes isomerize to the corresponding ketones and aldehydes, respectively. (Z)-Cyclooctene oxide undergoes the transannular reaction to give endo-cis-2-trimethylsiloxybicyclooctane.The reaction of 6-methyl-5-hepten-2-one oxide produces 2,2,6-trimethyl-3-trimethylsiloxy-3,4-dihydro-2H-pyran. 1,2-Methyl migration takes place in the reaction of (E)-3α-t-butyldimethylsiloxy-5α-pregnene 17α,20-oxide to afford 3α-t-butyldimethylsiloxy-17β-methyl-17α--18-nor-5α-androst-13(14)-ene. α-Pinene oxide gives trans-carveol trimethylsilyl ether.
- Murata, Sizuaki,Suzuki, Masaaki,Noyori, Ryoji
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p. 247 - 254
(2007/10/02)
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