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2A-Pyran

This residue is stirred at room temperature while 150 ml. of triethyl-amine [Ethanamine, A,A-diethyl] (Note 8) is added. Tricthylamine hydrobromide begins to precipitate soon after the addition is started, and the resulting slurry is refluxed gently for 15 minutes. It is then cooled to room temperature, and the insoluble material is removed by filtration and washed with benzene. Concentration of the combined filtrates under reduced pressure leaves an oily residue, which is dissolved in 600 ml. of ether. The ethereal solution is transferred to a 1-1. separatory funnel, washed with two 20-ml. portions of saturated aqueous sodium chloride, dried over anhydrous sodium sulfate, and filtered. Ether is removed with a rotary evaporator, and the resulting oil is distilled at reduced pressure. A forerun of 265 mg. is collected below 103° (22 mm,), and then 6.7 g. (70%) of 2A-pyran-2-one distils as a colorless oil, b.p. 103-111° (19-22 mm.) (Note 9). [Pg.50]

Preparation of 3-Substituted Dihydro-2(3f/)-furanones and 3-Substitutcd Tetrahydro-2A/-pyran-2-ones... [Pg.1026]

The ring closure of 1,5-keto-acids and their derivatives is a widely used strategy for the synthesis of 2A-pyran-2-ones <1984CHEC, 1996CHEC-II>. The 1,5-keto acid derivatives are typically formed in situ with concomitant ring closure to form 2//-pyran-2-ones. There are three main approaches to access the prerequisite 1,5-keto acid derivatives, namely (i) reaction of an ester enolate with a 2-acyl vinyl cation equivalent, (ii) the reaction of a ketone enolate... [Pg.545]

Reactions of Mo-Coordinated 2A/-Pyrans 138a with Organometallicas... [Pg.91]

Hetero-Diels-Alder reaction. 3,4-Bis(trimethylsilyl)-5,6-dihydro-2A/-pyrans are accessible from a catalyzed cycloaddition under very mild conditions. The diene is prepared in 44-47% yield from the reaction of l,4-ditosyloxy-2-butyne with trimethylsilylmethylmagnesium chloride. [Pg.62]

The infrared spectrum of this material was essentially identical to that of the redistillate, b.p. 115-118° (37 mm.). Reported physical constants for 2A-pyran-2-one are b.p. 206-209° (atmospheric pressure),... [Pg.106]

Ring opening of aziridines formally derived from 5,6-dihydro-2A/-pyran shows good regioselectivity involving preferential attack at C-4 of the pyran ring <97T1417>. [Pg.296]

A)-Mevalonolactone [mevalolactone, (/ )-tetrahy-dro-4-hydroxy-4-methyl-2A/-pyran-2-one]. [Pg.398]

CN [25-[2a(E),3p,4p,5a[2R, 3R (lR, 2R )]]].9-[[3-methyl-l-oxo-4-(tetrahydro-3,4-dihydroxy-5-[[3-(2-hydroxy-l-methylpropyl)oxiranyl]methyl]-2//-pyran-2-yl]-2-butenyl]oxy]nonanoic acid... [Pg.1376]

C,, H2c,N04SSi 106560-32-1) see Faropenem sodium [15-[lo(45, 6S ),2a,6p,8P,8att]]-4-n(l,1-dimethyl-ethyl)dimethylsilyl]oxy]-6-[2-(lA6,7,8,8a-hexahydro-8-hydroxy-2,6-dimethyl-l-naphthalenyl)ethyl]tetrahydro-2ff-pyran-2-one... [Pg.2364]

The reactions of 5,6-dihydro-2-methoxy-2H-pyran (101) with 1,3-dibromo-5,5-dimethylhydantoin in ether-methanol,137 and with ethanesulfenyl chloride,138 have been described by Baldwin and Brown. The former reaction gave a 2 1 mixture of the isomers 3/3-bromotetrahydro-2a ,4a-dimethoxypyran (102) and 3a-bromotetrahy-dro-2a,4/3-dimethoxypyran (103), respectively the structures and favored conformations of the isomers are shown. The reaction of ethanesulfenyl chloride with 5,6-dihydro-2-methoxy-2H-pyran (101)... [Pg.274]

The basic cycloadduct, butyl 2-methoxy-5,6-dihydro-2//-pyran-6-carboxylate 2a, can be reduced to 6-hydroxymethyl-2-methoxy-5,6-dihydro-2f/-pyran 2b. Both 5,6-dihydro- 2/f-pyrans 2a and 2b can be converted in several ways to sugars, cir-Hydroxy 1 ation or epoxidation, followed by basic (or acidic) opening of epoxides with various nucleophilic reagents leads to various 4-deoxyhexoses 3b [18], Dihydropyran 2b can be transformed in a... [Pg.617]

In Section III, the syntheses of 2-methoxy-5,6-dihydro-2//-pyrans 2a and 2b are described in racemic and in both enantiomeric forms, and by asymmetric synthesis. Also, the synthesis of l,2 5,6-di-0-isopropylidene-3-0-(2,3,4-trideoxy-a-r.-g/ycero-hex-2-eno-pyranosyl)-a-D-glucofuranose, a precursor of several disaccharides, is presented. [Pg.619]

Usually, the a-pyranic addition products (3) cannot be isolated because they isomerize immediately in a thermally allowed electrocyclic process affording acyclic dienones (4), which in many cases react further. Therefore, pyrylium salts 2A react with most nucleophiles as if they had the electronic structure 2B, and thus the pyrylium cation behaves as a useful synthon, namely the last vinylog in the series of acyl halides (Cj synthon) - p-halovinyl ketones (C3 synthon) - pyrylium (C5 synthon) [50, 51],... [Pg.214]

Yamashita, M., Inaha, T., Nagahama, M., Shimizu, T., Kosaka, S., Kawasaki, I., and Ohta, S. (2005) Novel stereoconvergent transformation of l,2a-disubstituted l,2,2a,8b-tetrahydro-3H-benzo[b] cydobuta[d]pyran-3-ones to 1,3-disubstituted l,2,4a,9b-tetrahydro-dibenzofuran-4-ols and its application to the second-generation synthesis of ( )-linderol A. Organic el Biomolecular Chemistry, 3, 2296-2304. [Pg.211]

Cyclopropan 1-Brom-l-ethoxy-El4a/3, 36 (0-SiR3 - Br) Pentan 5-Brom-2-oxo- Vll/2a, 785 Pentanal 2-Brom- V/4, 164 Pyran 2-Brom-tetrahydro- Vl/4, 379 Tetrahydrofuran 2-Brommethyl-E21e, 4787 (5-OR-en + NBS)... [Pg.217]

Propadien s. Allen Propan l-Cyclopropyl-2-methyl-l-oxo- VII/2a 1137, 1140 Propin 1-Butyloxy- V/2a, 108 4H-Pyran... [Pg.406]

Pyridin 4-Methyl-2-(2-tetrahydro-furyl)- E19a, 574 (Het. + Ether) 2-(2-Oxo-pentyl)- Vll/2a, 618 lH- 1,3-Dimethyl-3,4-dihydro- E7b/2,... [Pg.763]

Ethan 1,2-Dioxo-l-phenyl-2-(2-pyrryl)- VII/2a, 752 Indolo 2,3-c pyran l-Methyl-3-oxo-3,9-dihydro- E15/2, 1266 [3-CHj-COOH -indol +... [Pg.970]

Pyran 6-Methyl-3-(6-methyl-2-tetrahydro-pyranyliden)-2-oxo-tetrahydro- VII/2a, 500... [Pg.1054]

Propansaure 2,2-Dimethyl-3-oxo-3-phenyl- -ethylester VII/2a, 572 (-COC1 -> -CO-R), 600 (Reformatsky-Reakt.) XIII/2a, 829f. (Reformatsky-Reakt.) 2H-Pyran 2-Benzyloxy-5-hydroxy-6-methyl-5,6-dihydro- VI/la,l,... [Pg.1157]

Propen 1-Menthyloxy- E15/1, 294 (R2CH-COOR + Cl - /Base) 4H-Pyran 5-Butyl-2,6-dimethyl-5-ethyl-5,6-dihydro- Vl/4, 84 5>Undecin 7-Ethoxy- V/2a, 640... [Pg.1194]

H-Dibenzo[b,c( pyran-6-one, 9-methoxy-4a-methyl-2,3,4,4a-tetrahydro-2,3,7-trihydroxy-(2a,3p,4a[3)- ncHs 4249 ... [Pg.530]

H-Naphtho[2,1-b]pyran-2-ol, 3-ethenyldodeca hydro-3,4a,7,7, lOa-penta methyl-, [2S-(2a,313,4a3,6aa,10ap,10ba)]-... [Pg.596]

See other pages where 2A-Pyran is mentioned: [Pg.662]    [Pg.121]    [Pg.26]    [Pg.1180]    [Pg.662]    [Pg.121]    [Pg.26]    [Pg.1180]    [Pg.617]    [Pg.195]    [Pg.537]    [Pg.215]    [Pg.314]    [Pg.407]    [Pg.617]    [Pg.1101]    [Pg.1199]    [Pg.537]    [Pg.646]    [Pg.713]    [Pg.537]    [Pg.65]    [Pg.119]    [Pg.574]   
See also in sourсe #XX -- [ Pg.209 , Pg.212 , Pg.590 ]



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