Oxepin, 2, 7-dimethyl

Oxepin, 2-acetoxy-2,3,4,5-tetrahydro-thermal reactions, 7, 559 Oxepin, 3-chloro-synthesis, 3, 725 Oxepin, 2,3-dihydro-cycloaddition reactions, 7, 563 nucleophilic reactions, 7, 562 reduction, 7, 563 Oxepin, 2,5-dihydro-synthesis, 7, 578, 580 Oxepin, 4,5-dihydro-formation, 7, 579 reduction, 7, 563 synthesis, 7, 579 Oxepin, 2,7-dimethyl-NMR, 7, 552... 

Oxepin-2,7-dicarboxylic acid, dimethyl ester H NMR, 7, 552 <76TL1167)... 

Attempts have been made to catalyze the arrangement of 3-oxaquadricyclane to oxepins with transition-metal complexes.1 32 1 35 When dimethyl 2,4-dimethyl-3-oxaquadricyclane-l,5-dicarboxylate is treated with bis(benzonitrile)dichloroplatinum(II) or dicarbonylrhodium chloride dimer, an oxepin with a substitution pattern different from that following thermolysis is obtained as the main product. Instead of dimethyl 2,7-dimethyloxepin-4,5-dicarboxylate, the product of the thermal isomerization, dimethyl 2,5-dimethyloxepin-3,4-dicarboxylate (12), is formed due to the cleavage of a C O bond. This transition metal catalyzed cleavage accounts also for the formation of a 6-hydroxyfulvene [(cyclopentadienylidene)methanol] derivative (10-15%) and a substituted phenol (2-6%) as minor products.135 The proportion of reaction products is dependent on solvent, catalyst, and temperature. 

In a similar reaction, dimethyl 3-oxa-2,4-octanoquadricyclane-l,5-dicarboxylate gives the 6-hydroxyfulvene in 45% yield in addition to oxepin (15%) when bis(benzonitrile)dichloropal-ladium is used as catalyst.132 In the presence of silver(I) perchlorate the yield of 6-hydroxyful-vene reaches 85% whereas the thermal isomerization gives exclusively the oxepin (95% yield). 

When dimethyl 3-benzoxepin-2,4-dicarboxylate is reacted under controlled conditions (15 min) with hydrogen it is possible to isolate dimethyl l,2-dihydro-3-benzoxepin-2,4-dicarboxylate.17 Hydrogenation of 2-nitrodibenz[, /]oxepin-10-carboxylic acid in the presence of palladium on potassium carbonate results in the reduction of the nonaromatic C C double bond and the nitro group to give 2-amino-10,l l-dihydrodibenz[i,/]oxepin-10-carboxylic acid.107... 

Interestingly, in the inverse-electron-demand Diels-Alder reactions of oxepin with various enophiles such as cyclopentadienones and tetrazines the oxepin form, rather than the benzene oxide, undergoes the cycloaddition.234 236 Usually, the central C-C double bond acts as dienophile. Oxepin reacts with 2,5-dimethyl-3,4-diphenylcyclopenta-2,4-dienone to give the cycloadduct 6 across the 4,5-C-C double bond of the heterocycle.234 The adduct resists thermal carbon monoxide elimination but undergoes cycloreversion to oxepin and the cyclopenta-dienone.234... 

The reaction of oxepin with dimethyl 5-oxo-2,3-diphenylcyclopenta-l,3-diene-l,4-dicarboxy-late takes a different course. Two products 7 and 8 can be isolated, 7 is the [4 + 2] adduct of the cyclopentadienone across the central C-C double bond of the oxepin, the other, 8, is thought to be a [4+6] cycloadduct across the triene system of the oxepin.237 In boiling benzene, the [4 + 2] adduct 7 undergoes no cycloreversion, but rearranges to the tricyclo[5.3.02,4]deca-5,8-dien-10-one system.237 The [4+6] adduct, however, is stable under thermal conditions. 

The reaction of oxepin with dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate affords a 2 1 mixture of products 9 a and 10, whose formation can be rationalized by a [4+2] and a [4 + 6] cycloaddition, followed by nitrogen extrusion.235 With 2,7-dimethyloxepin, only dimethyl 6,8-dime-thy 1-2.4a-dihydrooxepino[4,5-c/]pyridazine-l,4-dicarboxy late (9b) as product of the [4 + 2] cycloaddition can be isolated.235 236... 

The reaction of oxepin and 2,7-dimethyloxepin with dimethyl 3-cyano-l,2,4-triazine-5,6-dicarb-oxylate takes the same course as the cycloaddition to the tetrazine. Two different addition products 11a and 12 are obtained in the case of oxepin, whereas dimethyloxepin yields only the [4 + 2] adduct lib.235... 

The aromatization of the oxepin structure can be accompanied by other acid-catalyzed reactions such as the hydrolysis of ketals. Dimethyl 11 -oxo-6-oxabicyclo[5.4.0]undeca-l (7),2,4-triene-2,3-dicarboxylate ethylene ketal reacts in the presence of trifluoroacetic acid to give the tetralone system 3.133... 

The light-induced reaction of pentacarbonyliron with oxepin or 2,7-dimethyloxepin results in the formation of small quantities (3-5 %) of a tricarbonyliron complex of the seven-mem-bered heterocycle.253,251 The main products are benzene (o-xylene) and phenol (2,6-dimethyl-phenol). When 1-benzoxepin is treated with pentacarbonyliron, the tricarbonyliron complex is obtained in 22% yield.254... 

The rearrangement of dimethyl 5-hydroxy-l-bcnzothiepin-3,4-dicarboxylate (9, R = OH), the first example of a thermal rearrangement of a thiepin derivative without loss of sulfur,12 is analogous to the oxepin-benzene oxide-phenol rearrangement (cf. Section D,l. Introduction and Section 1.2.5.1). This process is catalyzed by the acidic hydroxy substituent. In fact, if this functional group is modified by an in situ acetylation (R = OAc), the usual loss of sulfur occurs. 

Four naturally occurring secocularine alkaloids are known secocularine (228), secocularidine (229), norsecocularine (230), and noyamine (231). The first three belong to the 1,2-seco class possessing the characteristic N,N-dimethyl-aminoethyl side chain and oxepine system, and the fourth is a l,a-seco alkaloid... 

The 7-azaquadricyclane (77), like its precursor (12), shows evidence in the NMR spectrum of restricted rotation about the N-CO bond. All the 7-heteroquadricyclanes, 76-79, are thermolabile, and they rearrange very readily to the corresponding azepines (80) or oxepin (81). (In another instance the 7-oxabicyclo[4.1.0] valence-bond tautomer was obtained instead. ) In appropriate conditions the addition of acetylenic esters (methyl propiolate and dimethyl acetylene-dicarboxylate) competes successfully with the isomerization and gives the ca o-tricyclic adducts 82 or 83. " °... 

Carbon-13 shift of common non-aromatic heterocycles with endo- and exocyclic double bonds are reviewed in Table 4.66 [416-432], - Deshieldings of / -carbons induced by carbonyl groups in heterocyclic a, /1-enones due to (—)-M electron withdrawal (e.g. 2-pyrones, coumarins) and shieldings of [ carbons in cyclic enol ethers arising from (+ )-M electron release (e.g. 2,3-dihydrofuran and oxepine derivatives in Table 4.66) fully correspond to the effects described for the open-chain analogs. Outstandingly large shift values are observed for the lithiated carbon in cyclic a-lithium enol ethers (Table 4.66). In terms of its a and / carbon-13 shifts, 2,7-dimethyloxepine is also a typical enol ether [420], Further, 2,6-dimethyl-4-pyrone [421] and flavone [422] display similiar shift values for the a, /1-enone substructure. 

Both the monomethylbenzene oxide 153-155, which exists in dynamic equilibrium with a predominant oxepin component, and 2,7-dimethyloxepin (157), with almost no benzene oxide component (156), in equilibrium at ambient temperature, react with maleic anhydride and dimethyl acetylenedi-carboxylate to give the Diels-Alder adducts 175 and 176, respectively, resulting from reaction with the oxide form.8... 

Reaction of 117/-dibenzo[7/]thiepin-10-ones 135a and 135b with chloroacetone in the presence of base in dimethyl sulfoxide (DMSO) resulted in formation of O-alkylation products 136a and 136b in 23% and 8% yields, respectively (Equation 18) <2006JHC749>. On the other hand, oxepine analogs preferentially gave G-alkylation products. 

DIBENZ(b.e)OXEPIN-delta(sup 11(6H).gamma)-PROPYLAMINE, N.N-DIMETHYL-, HYDROCHLORIDE... 

Chemical Name 10,11-Dihydro-a,8-dimethyl-ll-oxodibenz[b,f]oxepin-2-acetic acid... 

Chemical Name N,N-Dimethyl-3-dibenz[b,e]oxepin-ll-(6H)-ylidene-l-propanamine hydrochloride... 

Oxepin 2-(2-Chlor-ethoxy)-7,7-dimethyl-3-fluor- E14a/1. 406 (Enol-ether + CHX3/Oxiran)... 

Diene cycloaddition reactions have frequently been used to characterize relatively unstable arene oxide-oxepins. The reactions of 1 with maleic anhydride or dimethyl... 

Enantiomeric analysis of a new antiinflammatory agent in rat plasma using a chiral p-cyclodextrin stationary phase" (71). The R,R S,S enantiomers of the investigational antiinflammatory agent trans-6,6a,7,10, 10a,ll-hexahydro-8,9-dimethyl-U-oxodibenz[b,e]-oxepin-3-acetic add (HOA) were resolved on the p-CD CSP after extraction from rat plasma. The mobUe phase was a mixture of 0.05 M potassium dihydrogenphosphate (pH 5.3) and methanol (35 65, v/v) the flow rate was 1.0 mL/min and the temperature was 22 1 C. The results of the study indicated that the inactive (—) enantiomer was cleared from the plasma more rapidly than the active (+) isomer. 

Diels-Alder dienes 1-Acetoxybutadiene. Butadiene. Cyclopentadiene. (rans,mins-l,4-Diacetoxybutadiene. 2,5-Di-o-anisyl-3,4-diphenylcyclopentadienone. 5,5-Dimethoxy-l, 2,3,4-tetrachlorocyclopentadienone. 2,3-Dimethylbutadiene. 6,6-Dimethylfulvene (see o-Acetoxy acrylonitrile). 2,4-Dimethyl-l,3-pentadiene (see Diethyl azodicarboxylate). 2,3-Diphenyl-butadiene. 1,3-Diphenylisobenzofurane (see Potassium I-butoxide). rrans,/nus-l,4-Diphenyl-butadiene. 1,3-Diphenylisobenzofurane. Hexachlorocyclopentadiene. Isobenzofurane. l-o-Nitrophenylbutadiene-1,3. Oxepin (see Diazabicyclo[3.4.0]nonene-S). Phenylcyclone. Piperylene. n-Pyrone (see also Methyl vinyl ketone). Tetrachlorocyclopentadienone. Tetra-chlorofurane. Tetraphenylcyclopentadienone. 

Dimethyl oxepine-4,5-dicarboxylate (50) exists mainly as the seven-membered-ring tautomer but reaction with diazomethane traps out the six-membered-ring tautomer. Photochemical deazetization followed by a second addition of diazomethane and deazetization gave the oxa-trishomobenzenes 51 and 52 cis/trans-isomers). ... 

Oxepin formation.1 A 1-1. three-necked flask fitted with a stirrer and thermometer and connected by means of a section of Gooch rubber tubing to a 125-ml. Erlenmeyer flask containing 33.2 g. of potassium /-butoxide (MSA Research Corp.) is charged with 42.1 g. of 4,5-dibromo-l,2-dimethyl-1,2-epoxycyclo-hexane (1) in 500 ml. of ether and cooled to 0°. The potassium /-butoxide is added... 

Ru(Tp)(PPh3)(MeCN)2]PFg has been employed as catalyst to produce l-iodo-2-naphthol in DMF and 2-iodobenzo[d]oxepin in benzene from l-(2/-iodoethynylphenyl)-2-propyloxirane. The solvent-dependent chemoselectivity has been ascribed to a solution equilibrium between ruthenium-Tt-iodoalkyne and ruthenium-2-iodovinylidene intermediates.66 The same ruthenium phosphine complex has been efficiently employed as catalyst in the nucleophilic addition of water, alcohols, aniline, acetylacetone, pyrroles, and dimethyl malonate to unfunctionalized enediynes that yielded functionalized benzene products in good yields (Fig. 8.6).67 [Ru(Tp)-(PPh3)(MeCN)2]PFg has been also found very active in catalytic benzannulation of l-phenyl-2-ethynylbenzenes in dichloroethane to afford phenanthrene.68... 

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