Flavan derivatives. XXIV. cis- and trans-3-Methoxyflavanones

1968 ◽  
Vol 21 (12) ◽  
pp. 3015 ◽  
Author(s):  
JW Clark-Lewis ◽  
RW Jemison ◽  
V Nair
Keyword(s):  
Hydrogen Bonding ◽  
Manganese Dioxide ◽  
Trifluoroacetic Acid ◽  
Trans Configuration ◽  
Trans Isomers ◽  
Cis And Trans ◽  
Cis Isomer

Oxidation of three 2,3-cia-3,4-cis-3-methoxyflavan-4-ols with active manganese dioxide gave the corresponding 2,3-cis-3-methoxyflavanones which were equilibrated in deuterochloroform containing trifluoroacetic acid to mixtures of cis- (c.33%) and trans-3-methoxyflavanones (c.67%). Tominaga's base-catalysed cyclization of 2'-hydroxy-α-methoxycha1cones to 3-methoxyflavanones has been found to yield the 2,3-trans isomers. The higher stability of the 2,3-trans-configuration of 3-hydroxy- flavanones (dihydroflavonols) compared with 3-methoxyflavanones is attributed to hydrogen bonding; no cis-isomer was detected when acid-catalysed epimerization of a trans-3-hydroxyflavanone was attempted. M.m.r. data are reported for the compounds described.

Sur la réduction de polyméthyldihydro-2,3 phénalènones-1 par l'hydrure de lithium et d'aluminium

1974 ◽  
Vol 52 (17) ◽  
pp. 3106-3112 ◽  
Author(s):  
E. Costakis ◽  
P. Canonne ◽  
R. St-Jean
Keyword(s):  
Trans Isomer ◽  
Lithium Aluminum Hydride ◽  
Aluminum Hydride ◽  
Considerable Extent ◽  
Lithium Aluminum ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
Cis Isomer ◽  
Steric Constraints

The reduction of some polymethyl-2,3-dihydro phenalen-1-ones by lithium aluminum hydride yields a mixture of cis and trans isomers; the percentage of each isomer depends to a considerable extent on its structure. Indeed, for some, the trans isomer predominates while for others the cis isomer is obtained in up to 88% yields. Moreover, in the particular case in which the trans isomer is formed in low yields, its preferred conformation is trans diaxial.The steric constraints which render certain transition states unfavourable during the attack of the hydride are discussed with the aid of spectroscopic data on the alcohols obtained. [Journal translation]

Alkylation Reactions of 2-Methylpropyl 3-(2-Methylpropoxy)-5-oxocyclohex-3-ene-1-carboxylate

1994 ◽  
Vol 47 (9) ◽  
pp. 1727 ◽  
Author(s):  
L Mokbel ◽  
GP Savage ◽  
GW Simpson
Keyword(s):  
Methyl Iodide ◽  
Trans Configuration ◽  
Equal Proportion ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Alkylation Reactions ◽  
Cis And Trans

The anion derived from 2-methylpropyl 3-(2-methylpropoxy)-5-oxocyclohex-3-ene-1-carboxylate was reacted with methyl iodide to give cis and trans isomers of 2-methylpropyl 6-methyl-3-(2-methylpropoxy)-5-oxocyclohex-3-ene-1-carboxylate. The reaction proceeded with high regioselectivity. A combination of n.m.r. experiments was used to determine that the major diastereoisomer was in a trans configuration. The dianion derived from 2-methylpropyl 3-(2-methylpropoxy)-5-oxocyclohex-3-ene-1-carboxylate methylated at C1 and C6 with a roughly equal proportion of cis and trans isomers. When treated with 1 equiv. of 1-bromo-3-chloropropane the same dianion alkylates at C1 to give 2-methylpropyl 1-(3-chloropropyl)-3-(2-methylpropoxy)-5-oxocyclohex-3-ene-1-carboxylate.

Ipso nitration. XVIII. Nitrationof 2-chloro-1,3,5-trimethylbenzene: nitration ipso to chlorine

1978 ◽  
Vol 56 (10) ◽  
pp. 1348-1357 ◽  
Author(s):  
Alfred Fischer ◽  
Sachdev Singh Seyan
Keyword(s):  
Acetic Acid ◽  
Ambient Temperature ◽  
Trifluoroacetic Acid ◽  
Boron Trifluoride ◽  
Boron Trifluoride Etherate ◽  
Trifluoroacetic Anhydride ◽  
Trans Isomers ◽  
Dimethyl Benzyl ◽  
Cis And Trans Isomers ◽  
Cis And Trans

Nitration of 2-chloro-1,3,5-trimethylbenzene in acetic anhydride gives the cis and trans isomers of 4-chloro-1,3,5-trimethyl-4-nitrocyclohexa-2,5-dienyl acetate (1, 21%), the cis and trans isomers of 3-chloro-2,4,6-trimethyl-4-nitrocyclohexa-2,5-dienyl acetate (2, 6%), and 2-chloro-1,3,5-trimethyl-4-nitrobenzene (73%). Diene 1 reacts with acidified aqueous acetone to form the corresponding dienol, acidified methanol to form the methyl ether, and hydrogen chloride to form the corresponding chloride. In acetic acid a mixture of 4-chloro-3,5-dimethyl-benzyl derivatives and 3-chloro-2,4,6-trimethylphenyl acetate are formed. In trifluoroacetic acid – trifluoroacetic anhydride and also in boron trifluoride etherate, 2-chloro-1,3,5-trimethyl-4-nitrobenzene is the predominant product. Diene 2 on reaction with acetic acid, acidified methanol, trifluoroacetic acid – trifluoroacetic anhydride, and boron trifluoride etherate gives 3-chloro-2,4,6-trimethylphenyl acetate. Some 2-chloro-4-nitromesitylene is obtained in trifluoromethanesulfonic acid. Diene 2 also gives the acetate on standing at ambient temperature or at −20 °C, and on pyrolysis. Diene 1 gives 4-chloro-3,5-dimethylphenylnitromethane on standing at ambient temperature or at −20 °C but a mixture of 2-chloro-1,3,5-trimethyl-4-nitrobenzene, chloromesitylene, and 3-chloro-2,4,6-trimethylphenyl acetate on pyrolysis.

cis/trans Isomers of Dimeric Dialkylaluminum and Dialkylgallium Hydrazides

2008 ◽  
Vol 63 (10) ◽  
pp. 1149-1154 ◽  
Author(s):  
Werner Uhl ◽  
Andreas Vogelpohl
Keyword(s):  
Solid State ◽  
Equilibrium Mixture ◽  
Trans Configuration ◽  
Trans Isomers ◽  
Tert Butyl ◽  
Hydrazine Derivatives ◽  
Piperidine Derivative ◽  
Cis And Trans Isomers ◽  
Gallium Hydride ◽  
Cis And Trans

AbstractThe reaction of diethylaluminum hydride with the hydrazine derivatives 1-aminopyrrole and 1- aminopiperidine afforded the corresponding dialkylaluminum hydrazides (1 and 2) by the release of elemental hydrogen. Both products are dimeric in the solid state. While 1 adopts a cis arrangement of the pyrrole groups, a trans configuration was determined for the piperidine compound 2. Only 1 gives an equilibrium mixture of cis and trans isomers in solution. Similar compounds (3 and 4) were obtained by the treatment of the same hydrazines with di(tert-butyl)gallium hydride. Both products exhibit the trans configuration in the solid state, but interestingly only the piperidine derivative 4 shows a cis/trans equilibrium in solution.

Synthese von Silicium-Phosphor-Ringen - Struktur eines cis-2.2.4.4-Tetrakis(silylamino)-1.3-diphospha-2.4-disilacyclobutans / Synthesis of Silicon-Phosphorus-Rings - Structure of a cis-2,2,4,4-Tetrakis(silylamino)-1,3-diphospha-2,4-disilacyclobutane

1983 ◽  
Vol 38 (12) ◽  
pp. 1557-1562 ◽  
Author(s):  
Uwe Klingebiel ◽  
Norbert Vater ◽  
William Clegg ◽  
Martin Haase ◽  
George M. Sheldrick
Keyword(s):  
Crystal Structure ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Molar Ratio ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
By Products ◽  
Cis Isomer

Fluorosilylphosphanes of the type R2SiFPHR′ (R = CHMe2, CMe3, NMeSiMe3; R′ = H, C6H5; 1-4) are obtained in the reaction of difluorosilanes with lithiated phosphanes in a molar ratio 1:1. Diphosphasilanes (5, 6) and a difluorosilylphosphane (7) are isolated as by-products. 1-4 react with n-C4H9Li to give cyclic silylphosphanes, LiF, and C4H10 (8-11). Dilithiated 5 reacts with F2PN(CMe3)SiMe3 to form of a four-membered SiP3-ring 12. The 31P NMR spectra of 9 and 11 show signal coalescence for the cis-and trans-isomers at room temperature. The crystal structure of the cis-isomer of 11 has been determined. The substituted ring 13 is prepared in the reaction of lithiated 9 and Me2SiF2

scholarly journals GEOMETRICAL ISOMERS OF RETINENE

1953 ◽  
Vol 36 (3) ◽  
pp. 415-429 ◽  
Author(s):  
Ruth Hubbard ◽  
Robert I. Gregerman ◽  
George Wald
Keyword(s):  
Absorption Band ◽  
Absorption Spectra ◽  
Present Theory ◽  
Trans Configuration ◽  
Trans Isomers ◽  
Geometrical Isomers ◽  
Main Absorption Band ◽  
Antimony Chloride ◽  
Cis Isomer

Five crystalline retinenes have been isolated, which have every appearance of being cis-trans isomers of one another. They are all-trans retinene; three apparently mono-cis isomers: neoretinenes a and b and isoretinene a; and isoretinene b, an apparently di-cis isomer. The absorption spectra of these substances display the relations expected of cis-trans isomers. The main absorption band is displaced 5.5 to 7 mµ toward shorter wave lengths for each presumptive cis linkage. Some of the presumptive cis isomers also display a cis peak at 255 to 260 mµ. All five substances yield an identical blue product on mixing with antimony chloride. All of them are converted by light to what appears to be an identical mixture of stereoisomers. Heat isomerizes them very slowly; only neoretinene b exhibits large changes on heating at 70°C. for 3 hours. The various isomers have been extensively interconverted by gentle procedures, and all of them have been converted to all-trans retinene. The present theory of cis-trans isomerism in carotenoids predicts the existence of four stable isomers of retinene. Instead we seem to have five—specifically three mono-cis forms where two are expected. There is no doubt that all these substances are closely related isomers of one another. The only point in question is whether they differ in part by something other than cis-trans configuration. One possibility, as yet little supported by evidence, is that isomerization between ß- and α-ionone rings may be involved. If, however, as seems more likely, all these substances are geometrical isomers of one another, some modification is needed in the present theory of configurational relationships in this class of compounds.

Reactions of Alkynes with Dicarbonyl(η-cyclopentadienyl)iridium

1979 ◽  
Vol 32 (10) ◽  
pp. 2147 ◽  
Author(s):  
PA Corrigan ◽  
RS Dickson
Keyword(s):  
Trans Isomer ◽  
Spectroscopic Data ◽  
Spectroscopic Properties ◽  
Organometallic Complexes ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
Related Reaction ◽  
Cis Isomer

Six organometallic complexes have been isolated from the reaction between (η-C5H5)Ir(C0)2 and hexafluorobut-2-yne at 120-160�. Both the cis and trans isomers of the σ-bridging alkyne complex (η C5H5)2Ir2(CO)2(CF3C2CF3) were obtained; the cis isomer is slowly transformed to the trans isomer at 160�. These complexes do not react further with alkynes. Two other products were identified as an iridiocyclobutenone complex and a iridiocyclopentadiene complex, viz.(η-C5H5){IrC(CF3)=C(CF3)CO}(CO) and (η-C5H5){IrC(CF3)=C(CF3)C(CF3)}(CO)These complexes are also inert to further reaction with hexafluorobut-2-yne, and the iridiocyclopentadiene complex could not be converted into the cyclopentadienone complex (η-C5H5)Ir{C4(CF3)4-CO). The spectroscopic properties of a product of formula (η-C5H5)Ir(CF3C2CF3)2(C4HF5) indicate it incorporates a 1-(2',2'-difluoroethenyl)-1,2,3,4,5-pentakis(trifluoromethyl)cyclopenta-2,4-diene ligand. The final product was formulated as (η-C5H5)Ir2(CO)3(CF3C2CF3)2H and five alternativestructures are consistent with the spectroscopic data. The related reaction between (η-C5H5)Ir(CO)2 and but-2-yne at 180� gives a small amount of hexamethylbenzene plus the maleoyl complex(η-C5H5){IrC(O)(Me=C(Me)C(O)}(CO).

Preparation of cis- and trans-[OsCl2(Me2SO)4], and X-Ray Crystal Structures of the All-S-Bound Isomers

1998 ◽  
Vol 51 (9) ◽  
pp. 807 ◽  
Author(s):  
Andrew M. McDonagh ◽  
Mark G. Humphrey ◽  
David C. R. Hockless
Keyword(s):  
Structural Study ◽  
Trans Isomers ◽  
Triclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
Group I ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
Cis Isomer

Efficient syntheses of the cis and trans isomers of [OsCl2(Me2SO)4] are reported. While a structural study of thetrans isomer confirms the spectroscopically assigned all-S-bound Me2SO configuration, a crystallographic determination of the cis isomer reveals a previously unheralded all-S-bound Me2SO geometry, in contrast to the spectroscopically inferred configuration predominant in solution which has one O-bound ligand. Fortrans-[OsCl2(Me2SO)4], crystals are tetragonal, space group I 4/m, with a 9·092(2), c 11·212(3) Å, Z 2, 566 unique reflections (34 parameters), converging at R 0·026 and Rw 0·032. For cis-[OsCl2(Me2SO)4], crystals are triclinic, space group P-1, with a 8·193(2), b 8·941(3), c 13·837(3) Å, α 79·77(2), β 79·91(2), γ 65·03(2)°, Z 2, 4152 unique reflections (173 parameters), converging at R 0·021 and Rw 0·018.

scholarly journals CIS-TRANS ISOMERS OF VITAMIN A AND RETINENE IN THE RHODOPSIN SYSTEM

1952 ◽  
Vol 36 (2) ◽  
pp. 269-315 ◽  
Author(s):  
Ruth Hubbard ◽  
George Wald
Keyword(s):  
Absorption Spectrum ◽  
Vitamin A ◽  
Wave Length ◽  
The Body ◽  
Trans Configuration ◽  
Trans Isomers ◽  
Geometrical Isomers ◽  
Violet Light ◽  
Cis Isomer

Vitamin A and retinene, the carotenoid precursors of rhodopsin, occur in a variety of molecular shapes, cis-trans isomers of one another. For the synthesis of rhodopsin a specific cis isomer of vitamin A is needed. Ordinary crystalline vitamin A, as also the commercial synthetic product, both primarily all-trans, are ineffective. The main site of isomer specificity is the coupling of retinene with opsin. It is this reaction that requires a specific cis isomer of retinene. The oxidation of vitamin A to retinene by the alcohol dehydrogenase-cozymase system displays only a low degree of isomer specificity. Five isomers of retinene have been isolated in crystalline condition: all-trans; three apparently mono-cis forms, neoretinenes a and b and isoretinene a; and one apparently di-cis isomer, isoretinene b. Neoretinenes a and b were first isolated in our laboratory, and isoretinenes a and b in the Organic Research Laboratory of Distillation Products Industries. Each of these substances is converted to an equilibrium mixture of stereoisomers on simple exposure to light. For this reaction, light is required which retinene can absorb; i.e., blue, violet, or ultraviolet light. Yellow, orange, or red light has little effect. The single geometrical isomers of retinene must therefore be protected from low wave length radiation if their isomerization is to be avoided. By incubation with opsin in the dark, the capacity of each of the retinene isomers to synthesize rhodopsin was examined. All-trans retinene and neoretinene a are inactive. Neoretinene b yields rhodopsin indistinguishable from that extracted from the dark-adapted retina (λmax· 500 mµ). Isoretinene a yields a similar light-sensitive pigment, isorhodopsin, the absorption spectrum of which is displaced toward shorter wave lengths (λmax· 487 mµ). Isoretinene b appears to be inactive, but isomerizes preferentially to isoretinene a, which in the presence of opsin is removed to form isorhodopsin before the isomerization can go further. The synthesis of rhodopsin in solution follows the course of a bimolecular reaction, as though one molecule of neoretinene b combines with one of opsin. The synthesis of isorhodopsin displays similar kinetics. The bleaching of rhodopsin, whether by chemical means or by exposure to yellow or orange (i.e., non-isomerizing) light, yields primarily or exclusively all-trans retinene. The same appears to be true of isorhodopsin. The process of bleaching is therefore intrinsically irreversible. The all-trans retinene which results must be isomerized to active configurations before rhodopsin or isorhodopsin can be regenerated. A cycle of isomerization is therefore an integral part of the rhodopsin system. The all-trans retinene which emerges from the bleaching of rhodopsin must be isomerized to neoretinene b before it can go back; or if first reduced to all-trans vitamin A, this must be isomerized to neovitamin Ab before it can regenerate rhodopsin. The retina obtains new supplies of the neo-b isomer: (a) by the isomerization of all-trans retinene in the eye by blue or violet light; (b) by exchanging all-trans vitamin A for new neovitamin Ab from the blood circulation; and (c) the eye tissues may contain enzymes which catalyze the isomerization of retinene and vitamin A in situ. When the all-trans retinene which results from bleaching rhodopsin in orange or yellow light is exposed to blue or violet light, its isomerization is accompanied by a fall in extinction and a shift of absorption spectrum about 5 mµ toward shorter wave lengths. This is a second photochemical step in the bleaching of rhodopsin. It converts the inactive, all-trans isomer of retinene into a mixture of isomers, from which mixtures of rhodopsin and isorhodopsin can be regenerated. Isorhodopsin, however, is an artefact. There is no evidence that it occurs in the retina; nor has isovitamin Aa or b yet been identified in vivo. In rhodopsin and isorhodopsin, the prosthetic groups appear to retain the cis configurations characteristic of their retinene precursors. In accord with this view, the ß-bands in the absorption spectra of both pigments appear to be cis peaks. The conversion to the all-trans configuration occurs during the process of bleaching. The possibility is discussed that rhodopsin may represent a halochromic complex of a retinyl ion with opsin. The increased resonance associated with the ionic state of retinene might then be responsible both for the color of rhodopsin and for the tendency of retinene to assume the all-trans configuration on its release from the complex. A distinction must be made between the immediate precursor of rhodopsin, neovitamin Ab, and the vitamin A which must be fed in order that rhodopsin be synthesized in vivo. Since vitamin A isomerizes in the body, it is probable that any geometrical isomer can fulfill all the nutritional needs for this vitamin.

PREPARATION AND STEREOCHEMISTRY OF 1,2-O-(2′-HYDRO0XY-ETHYLIDENE)- AND 1,2-O-(HYDROXYISOPROPYLIDENE)-GLYCEROLS

1966 ◽  
Vol 44 (15) ◽  
pp. 1787-1793 ◽  
Author(s):  
P. A. J. Gorin ◽  
T. Ishikawa
Keyword(s):  
Hydrogen Bonding ◽  
Chemical Synthesis ◽  
Infrared Absorption ◽  
Hydroxyl Group ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Absorption Studies ◽  
Cis And Trans

The cis- and trans-isomers of 1,2-O-(2′-hydroxyethylidene)-glycerol (I and II) and 1,2-O-(hydroxyisopropylidene)-glycerol (V and VI) were prepared and their configurations assigned by stereospecific chemical synthesis. Equilibration of 1,2-O-(2′-cis-hydroxyethylidene)-L-glycerol (I) in acidified chloroform gave mainly 1,3-O-(2′-cis-hydroxyethylidene)-glycerol (III). In the 1,2-O-(hydroxyisopropylidene)-glycerol series, equilibration data and infrared absorption studies showed that hydrogen bonding of the O-(hydroxyisopropylidene) hydroxyl group was more pronounced in the cis-isomers.

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