6-Nitro-7-trimethylsilyloxy

Furan, 2,5-bis(trimethylsilyloxy)-cycloaddition reactions, 4, 625 Diels-Alder reactions, 4, 77 synthesis, 1, 417 Furan, bromo-dipole moments, 4, 553 Furan, 2-bromo-electron diffraction, 4, 537 reactions, 4, 78 synthesis, 4, 604 Furan, 3-bromo-electron diffraction, 4, 537 Furan, 2-bromomethyl-5-nitro-reactions... 

Node and co-workers have found that the Diels-Alder reaction of nitroalkenes v/ith 1-methoxy-3-trimethylsilyloxy-l,3-butadiene (Danishefsky s dienesi exhibit abnormal exo-se-lecdvity Electrostadc repulsion between the nitro and the silyloxy group of the diene induces this abnormal exc-selecdvity (Tq 8 10 This selecdve reacdon has been used for the asymmetric synthesis of various naniral products as shovm in Scheme 8 6... 

In contrast, the titanium(IV)-catalyzed condensation of l-(trimethylsilyloxy)cydohexene and ( )-3-(2-nitro-l-propenyl)furan proceeded in the reverse stereochemical sense and gave three diastereomeric 1,2-oxazine 2-oxides lb, 2b and 3b in a ratio of 1 4 1. The major diastereomeric adducts 2b and lb were converted to the. syn-ketonc 4b upon hydrolysis16. 

The condensation of arylsulfonyl acetonitriles 369a-c with 22a proceeds via addition of the in-situ formed anion 370 to the arylsulfonyl acetonitriles 369 to afford the dimers 371, in 69-94% yield, and hexamethyldisiloxane 7 [136]. Furthermore, y9-dicarbonyl compounds such as ethyl acetoacetate 372 a or ethyl benzoyl-acetate 372b are O-silylated by 22 a or 22 c to rather stable alkyl 3-O-trimethylsilyl-oxycrotonoate 373a and alkyl 3-0-trimethylsilyloxy-3-phenyl acrylate 373b [130]. Aliphatic nitro compounds such as nitromethane are O-trimethylsilylated and further transformed into oligomers [132] (cf Section 7.6) and are thus unsuitable reactants for silylation-C-substitutions (Scheme 4.50). 

O-Trimethylsilyl nitronates 1036 have been used in fluoride-catalyzed aldol-type condensations with aldehydes and ketones to give a-trimethylsilyloxy-nitro com-... 

Trimethylsilyloxy-cyclohexen reagiert mit Nitronimn-tetrafluoroborat in Acetonitril bei — 25° mit 47% Ausbeute zu 2-Nitro-l-oxo-cyclohexan2 (mit Nitryl-chlorid wird dagegen... 

In analoger Weise erhalt man aus l,3-Dimethyl-2-trimethylsilyloxy-cyclohexen 2,6-Dime-thyl-2-nitro-l-oxo-cyclohexan (41%) bzw. aus 1-Trimethylsilyloxy-cyclopenten 2-Nitro-l-oxo-cyclopentan2 (95%). 

Die Addition von Nitro-alkanen an 1 -(1 -Alkenyl)-1 -trimethylsilyloxy-cyclopropane in me-thanolischer Benzyl-trimethyl-ammonium-hydroxid-Losung (Triton B) liefert unter Ring-offnung 7-Nitro-4-oxo-alkansaure-Derivate z.B.1 ... 

Induziert durch einen OberschuB an Dichlor-diisopropyloxy-titan reagieren verschiedene -Nitro-1-alkene mit 1-Trimethylsilyloxy-cyclohexen in Dichlormethan bei — 90° zu bicyclischen Nitronaten, die mit katalytischen Mengen an Kaliuinfluorid in Methanol anti- bzw., syrt-2-(2-Nitro-ethyl)-l-oxo-cyclohexane liefem (55-81%)4 ... 

Propansaure 2-(4-Nitro-phenyl)-2-trimethylsilyloxy- -nitrilE5,1421 (R-CHO + R2Si —CN)... 

In a synthesis of the tricychc skeleton of FR901483 (45), Bonjoch and Sole reported a TMG (3) promoted conjugate addition reaction of nitroalkane to methyl acrylate. Reaction of methyl acrylate (40) and nitro acetal 41 [9,10], obtained from Diels-Alder reaction between nitroethylene and 2-(trimethylsilyloxy)-l,3-butadiene, gave nitro ester 42 in 71% yield. The ester 42 was further converted to the spiro compound 43, and a palladium promoted cyclization reaction led to the azatricyclic skeleton 44 (Scheme 7.7). 

The oxime RC =NOH)NHCH=Ph (R = p-O NCoH ) undergoes oxidative cyclization to 3-p-nitro-phenyl-5-phenyl-l,2,4-oxadiazole 71 under the influence of potassium permanganate (93ZOB2635). 3-Trimethylsilyloxy-l,2,5-oxadl-azoles 72 react with triethyl orthoformate to afford comparable amounts of 3-ethoxy-oxadiazoles 73 and the novel 1,2,5-oxadiazo-... 

A review (37 refs.) on the application of molecular orbital calculations to the stereoselectivity of addition reactions of nitro-enitol derivatives has been published in Japanese. Cycloaddition of 1-acetoxy- or 1-trimethylsilyloxy-butadiene to l,2-dideoxy-l-nitro-D-g/ co-hept-l-enitol tetraacetate gave mainly the cyclohexane derivatives 41. Additions of alcohols, carbon radicals and phosphoiyl... 

Although commercially available, 1-trimethylsilyloxy-1,3-butadiene (1) can be easily prepared by silylation of crotonaldehyde. It has often been used as a reactive diene in Diels-Alder reactions. For example, reaction with dimethyl acetylenedicarboxylate (2) affords the cyclohexadiene diester (3) in 68% yield. This initial Diels-Alder adduct can be converted into two different aromatic products by the proper choice of conditions namely, thermal elimination affords the phthalate (4), while oxidation produces the phenol (5), hoth in good yield (eq 1). Reaction with methyl 3-nitroacrylate (6) followed hy hydrolysis of the initial adduct (7) and elimination of the -nitro group leads to the cyclohexadienol (8) (eq 2). Many other Diels-Alder reactions of this type have been carried out using (1), as shown in Table 1. In general, the endo adduct is favored, especially at lower temperatures. 

The reaction of Danishefsky s diene (6CPC, 12 and 24 h, respectively) with la using the three ILs cited in the before p>aragraph yielded 5-hydroxyibenzofuran 16 in reasonable yield (Figure 4). Similarly to the reactions with isoprene and l-trimethylsilyloxy-l,3-butadiene, the best yield was observed with EAN (ca 65%). The product obtained in the reactions with diene 7 resulted from the aromatization of the nitro-adducts promoted by the loss of the nitro and methoxyl groups as nitrous acid and methanol, respectively. The intermediate that suffered nitrous acid extrusion and retained the methoxy group was not detected in any case. 

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