1.4- Cyclohexadiene 1- methoxy

The aqueous [4+2] cycloaddition reaction of 1,4-naphthoquinones 115 with methoxy cyclohexadiene performed in the presence of bovine serum albumin (BSA) is one of the first examples of protein-promoted Diels Alder reactions [79]. Some results are reported in Table 4.18. The globular protein does not affect the regioisomer ratio of adducts. The highest enantiomeric excess was obtained in the cycloaddition of juglone 115 (R = H) with 1-methoxy-1,3-cyclohexadiene 116. 

Toluol bildet bei der Reduktion mit Natrium/HMPT/Athanol (Natrium Athanol = 1 1) selektiv Methyl-cyclohexene3, wahrend mit anderen Systemen zumeist Me-thyl-cyclohexadiene entstehen3. Aus Anisol wird mit Lithium/HMPT zu 40% d.Th. 3-Methoxy-cyclohexadien-(l,4) erhalten4. 

Diacetoxylation of various conjugated dienes including cyclic dienes has been extensively studied. 1,3-Cyclohexadiene was converted into a mixture of isomeric l,4-diacetoxy-2-cyclohexenes of unknown stereochemistry[303]. The stereoselective Pd-catalyzed 1,4-diacetoxylation of dienes is carried out in AcOH in the presence of LiOAc and /or LiCI and beiizoquinone[304.305]. In the presence of acetate ion and in the absence of chloride ion, /rau.v-diacetox-ylation occurs, whereas addition of a catalytic amount of LiCl changes the stereochemistry to cis addition. The coordination of a chloride ion to Pd makes the cis migration of the acetate from Pd impossible. From 1,3-cyclohexadiene, trans- and ci j-l,4-diacetoxy-2-cyclohexenes (346 and 347) can be prepared stereoselectively. For the 6-substituted 1,3-cycloheptadiene 348, a high diaster-eoselectivity is observed. The stereoselective cij-diacetoxylation of 5-carbo-methoxy-1,3-cyclohexadiene (349) has been applied to the synthesis of dl-shikimic acid (350). 

C. 7 ricar6oni/Z[( 1,2,3,4,5-jj)-l-and 2-methoxy-2,4 -cydohexadien-l-yl]-irTriphenylmethyl tetrafluoroborate [Methylium, triphenyl-, tetrafluoroborate] (34 g., 0.103 mole) (Note 20) is dissolved in a minimum volume of dichloromethane and 18 g. (0.072 mole) of tricarbonyl (1- and 2-methoxy-l,3-cyclohexadiene)iron dissolved in a like volume of dichloromethane is added. The resulting dark solution is left for 20-30 minutes and then added with stirring to three times its volume of ether (Note 21). The precipitate is collected and washed with ether to 5ueld 21-22 g. (87-91%) of product as yellow solid (Note 19). 

The infrared spectrum of the l-methoxy-l,4-cyclohexadiene shows the absence of strong aromatic absorption at 1600 cm.the ultraviolet spectrum shows absence of absorption at 270 nm., indicating absence of the conjugated isomer. 

Iron pentacarbonyl and l-methoxy-l,4-cyclohexadiene react as shown by Birch and oo-workera, but in dibutyl ether this solvent has been found superior. The tricarbonyl(methoxy-l,3-cyclohexadiene)iron isomers undergo hydride abstraction with triphenylmethyl tetrafluoro-borate to form the dienyl salt mixture of which the 1-methoxy isomer is hydrolyzed by water to the cyclohexadienone complex. The 2-methoxy isomer can be recovered by precipitation as the hexafluoro-phosphate salt. By this method the 3-methyl-substituted dienone complex has also been prepared from l-methoxy-3-methylbenzene. The use of the conjugated 1-methoxy-1,3-cyclohexadiene in Part B led to no increase in yield or rate and resulted chiefly in another product of higher molecular weight. An alternative procedure for the dienone is to react tricarbonyl(l,4-dimethoxycyclohexadiene)iron with sulfuric acid. ... 

Yamamoto et al. have reported a chiral helical titanium catalyst, 10, prepared from a binaphthol-derived chiral tetraol and titanium tetraisopropoxide with azeotropic removal of 2-propanol [16] (Scheme 1.22, 1.23, Table 1.9). This is one of the few catalysts which promote the Diels-Alder reaction of a-unsubstituted aldehydes such as acrolein with high enantioselectivity. Acrolein reacts not only with cyclo-pentadiene but also 1,3-cyclohexadiene and l-methoxy-l,3-cyclohexadiene to afford cycloadducts in 96, 81, and 98% ee, respectively. Another noteworthy feature of the titanium catalyst 10 is that the enantioselectivity is not greatly influenced by reaction temperature (96% ee at... 

Chemical Name 7-[ (Amino-1,4-cyclohexadien-1-yl-acetyl)amino] -3-methoxy-B-oxo-5-thia-1 -azabicyclo [4.2.0] -oct-2-ene-2-carboxylic acid... 

METHOXY-2,4-CYCLOHEXADlEN-l-YL] -5,5-DIMETHYL-l, 3-CYCLO-HEXANEDIONE]lRON,57, 16 TRICARBONYL [(1,2,3,4,5-n)-2-METH-OXY-2.4-CYCLOHEXADIENE-1-YL ] -IRON(l+)HEXAFLUOROPHOS-PHATE(l-), 57, 107... 

Li, S. M. Lundquist, K. Soubbotin, N. Stomberg, R. 2-Bromo-4-[2-bromo-( )-propy-lidene]-6-methoxy-2,5-cyclohexadien-l-one. Acta Crystallogr. 1995, 51, 2366-2369. 

The bora-2,5-cyclohexadienes 25, 43, and 44 have been used in experimental studies. Photochemical reaction of 25 and 43 with Fe(CO)s produces the robust complexes 45 (29) and 46 (92) with 7)5-divinylborane structures (92), whereas thermally induced complex formation of 44 with Fe2(CO)9 is accompanied by ligand isomerization and affords complex 47 (67). We note in passing that S(UB) = 38.8 ppm for 47 is at rather low field. The only strictly comparable boraolefin known is l-methoxy-6-(trimethylsilyl)bora-2,4-cyclohexadiene [8(nB) = 47.1 ppm] (26). On this basis, the high field shift upon complexation (only 8.3 ppm) indicates weak Fe-B interaction. 

Methoxy-3 -methyl-5,6-benzo-6H-1,2-dioxin, 3313 3-Methoxy-4-methyl-5,6-benzo-6//-l,2-dioxin, 3314 l-(c/s-Methoxyvinyl)-l,4-endoperoxy-2,5-cyclohexadiene, 3153 Methyltrilluoromethyldioxirane, 1102... 

Anodic oxidation of halogenated tyrosines was studied in connection with some sponge metabolites (cavemicolin model compounds). The methyl exter of 3,5-dibromotyrosine afforded four different products in a 41 10 26 23 ratio with 23% overall yield as a result of equilibration. (Scheme 44) [93JCS(P2)3117], A related compound was obtained as a mixture of stereoisomers 56 from a Diels-Alder reaction between N-acetyldehydroalanine methyl ester and l-methoxy-l,3-cyclohexadiene (87TL2371). 

Vinyl ethers were reductively cleaved by lithium, sodium or potassium in liquid ammonia especially in the absence of alcohols (except terf-butyl alcohol) A mixture of l-methoxy-1,3- and l-methoxy-l,4-cyclohexadiene gave in this way first methoxycyclohexene and, on further reduction, cyclohexene Reductive cleavage of a-alkoxytetrahydrofurans and pyrans will be discussed in the chapter on acetals (p. 104). 

The retrosynthetic analysis of the 2-oxygenated carbazole alkaloids, 2-methoxy-3-methylcarbazole (37), O-methylmukonal (glycosinine) (38), 2-hydroxy-3-methylcar-bazole (52), and mukonal (53) based on the molybdenum-mediated approach led to the molybdenum-complexed cation (663) and 3-methoxy-4-methylaniline (655) as precursors (Scheme 5.51). The cationic molybdenum complex, dicarbonyl (ri -cyclohexadiene)(r -cyclopentadienyl)molybdenum hexafluorophosphate (663), required for the electrophilic substitution, was easily prepared quantitatively through known literature procedures (586,587). 

Cyclohexadienes are available by the methodology of Birch, and the reactions of l-methoxy-, 1,3-dimethoxy-, l,3-bis(trimethyl-silyloxy)-, and l-methoxy-4-methyl-l,3-cyclohexadiene with a number of 1,4-benzoquinones have been investigated. Acid treatment of the adducts and subsequent dehydrogenation provides a synthesis of 2-dibenzofuranols. Thus the adduct 159 (Scheme 41) from 1,4-benzoquinone and 1,3-dimethoxy-1,3-cyclohexadiene, on treatment with a trace of concentrated hydrochloric acid in ethanol at room temperature, affords the tetrahydrodibenzofuranone 161. When the adduct 159 is heated under reflux in aqueous methanol, the reaction can be arrested at the dihydrodibenzofuran 160. The tetrahydrodibenzofuranone 161 on dehydrogenation with palladized charcoal affords 2,7-dibenzofurandiol. ... 

Die angegebenen Ausbeutcn beziehen sich auf den Umsatz von 6-substituierlem 6-Methoxy-3-oxo-l,4-cyclohexadien. Es ist jedoch auch moglich, eine Eintopfreaktion dirckt ausgchcnd von den substituierten Phcnolcn durchzufuhren ... 

OCHj F 100 -60 0,5 4-Fliu>r-l-methoxy-2-nitro- benzol + 3-Fluor-3-nitro-6-oxo-l,4-cyclohexadien 94 6 61 1... 

Iron, tricarbonyl[2-[(2,3,4,5-i))-4-methoxy-2,4-cyclohexadien-l-yl]-5,5-dimethyl-1,3-cyclohexane one] -]... 

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