2.5- Dimethoxy-3- pyrazine

A special case, demonstrating the high versatility of the bis-lactimether method , utilizes the symmetrical derivative obtained from L-leucine, i.e, (2S,5S)-2,5-dihydro-3,6-dimethoxy-2,5-bis(2-methylpropyl)pyrazine (1)14. [Pg.1048]

With chiral racemic oxiranes one enantiomer reacts faster than the other the degree of kinetic resolution is very high for L-valine/alanine-based dialkoxydihydropyrazines. For example, in the reaction of one equivalent of (2.S )-2,5-dihydro-2-isopropyl-3,6-dimethoxy-5-methyl-pyrazine (1, R1 = CH3) with two equivalents of fW-(//,/ )-2,3-dimethyloxirane (R2,R4 = CH3 R = H) virtually only the (2//,3/ )-oxirane enantiomer reacts with the lithiated dihydropyrazine to give exclusively the (l /, 2/, 2 / )-configuratcd adduct i.e., (2/ ,5S)-2,5-dihydro-5-isopropyl-3,6-dimethoxy-2-[(l/ ,2/ )-2-(2-methoxyethoxymethoxy)-l-methylpropyl]-2-methylpyrazine, entry 7. Likewise, kinetic resolution (intramolecular) occurs upon reaction with rac-7-oxabicy-clo[4.1.0]heptane (entry 8). [Pg.1051]

S,5K)-2.5Dihvdro-2-isopr<>pvl-3,6-dimethoxy-5- 2-(2-nicthox ethoxymethoxy)alkyi pyrazines 2 General... [Pg.1052]

Dimethoxy-3,6-diisopropyl- pyrazine OCH3 -c3H7 och3 C3H7... [Pg.226]

Treatment of the /3-lactam, 3,3-dimethoxy-l-p-methoxyphenyl-4-p-methoxyphenyliminomethyl-2-azetidinone (3, R = H), with stannous chloride in dichloromethane for 20 h gave 1,4-bisf/ -methoxyphenyl)-2,3(l//,4//)-pyrazine-dione (5, R = H) in 95% yield by ring expansion via the acetal (4) 874 the 4-methy-lated substrate (3, R = Me) likewise gave 1,4-bisf p-methoxyphenyl)-5,6-dimcthyl-2,3(lH,4tf)-pyrazinedione (5, R = Me) (99%).874 cf-1740... [Pg.48]

Isopropyl-3,6-dihydro-2,5(l//,4//)-pyrazinedionc (74) gave a separable 1 2 mixture of 6-isopropyl-5-methoxy- (72) and 3-isopropyl-5-methoxy-3,6-dihydro-2(l//)-pyrazinonc (73) [Me3OBF4 (1 mol), CH2C12, 20°C, N2, 6 h 60% (mixture)] or 2-isopropyl-3,6-dimethoxy-2,5-dihydro pyrazine (75) [Me3OBF4 (excess), CH2C12, 20°C, N2, 4 days 85%].1351... [Pg.202]

Although both types of pyrazine ethers are easily made, only the nuclear alkoxypyrazines can be used as substrates for nucleophilic displacement reactions. Some epoxides are included in the present discussion. Shape details of cis- and tra y-2,5-dimethoxy-3,6-diphenyl-3,6-dihydropyrazine have been elucidated by X-ray analysis.1243... [Pg.217]

Ethylthio-2-pyrazinecarbonitrile 6-Ethylthio-2-pyrazinecarbonitrile 6-Ethylthio-2-pyrazinecarbothioamide 3-Ethylthio-2-pyrazinecarboxamide 6-Ethylthio-2-pyrazinecarboxamide 3-Ethylthio-2-pyrazinecarboxylic acid 6-Ethylthio-2-pyrazinecarboxylic acid 3-Ethylthio-2,5-pyrazinedicarboxamide 2-Ethylthiopyrazine 1-oxide 2-Ethyl-3,5,6-trimethylpyrazine 2-Ethyl-3,5,6-triphenylpyrazine 2-Ethyl-3-vinylpyrazine 2-Ethynyl-3,6-dimethylpyrazine 2-Ethynyl-3-methylpyrazine 2-Fluoro-5,6-dimethoxy-3-methylpyrazine 2- Fluoro- 5,6-dimethoxypyrazine 2-Fluoro-3,6-dimethylpyrazine 2-Fluoro-3-(l-hydroxyethyl)pyrazine 2-Fluoro-3-iodopyrazine 2-Fluoromethyl-5-methyl-3,6-diphenylpyrazine 2- Fluoro- 5-phenylpyrazine 2-Fluoro-3-phenylthiopyrazine... [Pg.423]

Pyrazin 3,6-Dimethoxy-2,5-dime-thyl-2-hydroxymethyl- E21b,... [Pg.662]

Pyrazin 3,6-Dimethoxy-2-isopropyl-5-(l -methyl-2-nitro-ethyl)-2,5-dihydro- E16d, 441 (Michael-Addition)... [Pg.1069]

Dimethoxy(or diethoxy)-3,6-dimethylpyrazine 1,4-dioxide with phosphoryl chloride have been shown to give 2,5-bis(chloromethyl)-3,6-dimethoxy(or diethoxy)-pyrazine (756), 3-ethoxy-2,5-dimethylpyrazine 1-oxide gave 2-chloro-5-ethoxy-... [Pg.115]

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