Tetraene

Epoxide opening with nucleophiles occurs at the less substituted carbon atom of the oxlrane ting. Cataiytic hydrogenolysis yields the more substituted alcohol. The scheme below contains also an example for trons-dibromination of a C—C double bond followed by dehy-drobromination with strong base for overall conversion into a conjugated diene. The bicycKc tetraene then isomerizes spontaneously to the aromatic l,6-oxido[l0]annulene (E. Vogel, 1964). 

The linear dimerization of substituted conjugated dienes is difficult, but the Pd-catalyzed intramolecular dimerization reaction of the 1,3,9,11-tetraene 13 gives the 3-propenylidene-4-allylpiperidine derivative 14, which has the 1,3,7-octatriene system. The corresponding 1,3,8,10-tetraene also affords the 3-pro-penylindene-4-allylcyclopentane derivative[18]. 

The skeletal rearrangement of various strained cyclic compounds is carried out with a catalytic amount of soluble complexes of PdCl2. Namely, the rearrangements of bulvalene (67) to bicyclo[4.2.2]deca-2,4,7,9-tetraene (68)[54], cubane (69) to cuneane (70)[55], hexamethyl Dewar benzene (71) to hexa-methylbenzene (72)[56], and 3-oxaquadricyclanes[57] and quadricyclane (73) to norbornadiene[58-60] take place mostly at room temperature. Reaction of iodocubane (74) with a terminal alkyne catalyzed by Pd(0) and CuBr unexpectedly affords an alkynylcyclooctatetraene 75, without giving the desired cubylalkyne 76. Probably the rearrangement is a Pd-catalyzed reaction[61]. 

Cyclooctatetraene is relatively stable but lacks the special stability of benzene Unlike benzene which we saw has a heat of hydrogenation that is 152 kJ/mol (36 kcal/mol) less than three times the heat of hydrogenation of cyclohexene cycloocta tetraene s heat of hydrogenation is only 26 kJ/mol (6 kJ/mol) less than four times that of CIS cyclooctene... 

The April 1993 issue of the Journal of Chemical Educa tion ipp 291-293) contained an article about cycloocta tetraene entitled Don t Stop with Benzene Keep Going with Cyclooctate traene appeared in the Jan uary 2000 issue (pp 55-57)... 

Other aromatic ions include cyclopropenyl cation (two rr electrons) and cycloocta tetraene dianion (ten tt electrons)... 

Section 11 18 Although cychc conjugation is a necessary requirement for aromaticity this alone is not sufficient If it were cyclobutadiene and cycloocta tetraene would be aromatic They are not... 

The sex attractant of the female winter moth has been identified as the tetraene CH3(CH2)8CH=CHCH2CH=CHCH2CH=CHCH=CH2 Devise a synthesis of this material from 3 6 hexadecadien 1 ol and allyl alcohol... 

Natamycin. Natamycin or pimaricin (2) is a polyene with only four conjugated double bonds. This tetraene is obtained from Streptomjces natalensis. Like the other polyenes, pimaricin induces release from cells with membranes containing 20—40 mol % ergosterol. This is also the ergosterol concentration in the membrane of Saccharomjces cerevisiae. 

Thiacyclotrideca-2,4,10,12-tetraene-6,8-diyne 1,1-dioxide, 5,10-dimethyl- HNMR, 7, 717 (75JA640)... 

Thiacyclotrideca-2,4,10,12-tetraene-6,8-diyne 1 -oxide, 5,10-dimethyl- HNMR, 7, 717 (75JA640) 4-Thia-2,6-diazabicyclo[3.2.0]heptane-2-carboxylic acid, 7-OXO-, t-butyl ester X-ray, 7, 349 (B-72M151201) 5H-2aA -Thia-2,3-diazacyclopent[cd]indene, 2,3-dimethyl-6,7-dihydro-X-ray, 6, 1054 (72ACS343)... 

The indicator was prepared by the method of Oiehl and Einhorn. A solution of 5 g of sodium hydroxide in 50 mL of water and 40 ml of ethanol is prepared in a 250-mL Erlenmeyer flask. To this is added a solution of 1.64 ml (0.025 mol, 1.45 g) of acetone in 6.3 mL (0.050 mol, 5.6 g) of freshly distilled cinnamaldehyde (Note 1). This mixture is stirred thoroughly at room temperature for 30 min. The resulting voluminous yellow precipitate is filtered with suction, washed with 100 mL of water, and dried, affording 6.5 g of l,9-diphenylnona-l,3,6,8-tetraen-5-one. Recrystallization from 200 mL of hot 9511 ethanol gives 3.5 g of yellow crystals, mp 142-143 C (lit mp 142°C). This indicator is also available from Aldrich Chemical Co. 

The preparations are much simplified if a stoichiometric amount of hydrogen halide is added using an indicator to determine the end point. We have found that 1,9-diphenylnona-1,3,6,8-tetraen-5-one (dicinnamalacetone) is of appropriate basicity to detect excess anhydrous hydrogen halides in organic solvents including chloroform, dichloromethane, benzene, toluene, acetic acid, and acetone (but not in alcohols). The reaction between the... 

Heidelberger. This tetraene has evoked a eonsiderable amount of interest both as regards its eonstitution and as a primary material for polymerisation. It has been prepared again from psewdopelletierine by Cope and Overberger, ° who record m.p. -5-8 to -5-4°, 1-5342, and describe... 

Methoxyestra-l,3,5(10),14-tetraen-17-one. A solution of 9.3 g (0.0328 mole) of 3-methoxyestra-l,3,5(10),14-tetraen-17)S-ol in 300 ml of methylene dichloride is added at a rapid dropwise rate to a stirred suspension of 46.5 g (0.18 mole) of the dipyridine-chromium VI complex in 800 ml of methylene dichloride at room temperature. The mixture is stirred 45 min and then filtered. The residue is washed with ethyl acetate and the organic layers are combined. Water is added to the filtrates and sufficient ethyl acetate is added to make the organic layer less dense than water. After the organic layer is washed with water it is dried over sodium sulfate and concentrated to leave... 

The 13-ethyl-17-ketones, i.e., (63), have been found to be considerably less reactive than their 13-methyl counterparts towards acetylenic nucleophiles. The difference is attributed to the additional steric hindrance provided by the ethyl group. An attempt to introduce an ethynyl group into mc- 2>-isopropyl-3-methoxygona-l,3,5(10)-trien-17-one was unsuccessful even in ethylenediamine at 50°. However ethynylation of rac-13-isopropyl-3-methoxygona-1,3,5(10),8(14)-tetraen-17-one proceeded smoothly at room temperature to afford the 17a-ethynyl compound in 60% yield. ... 

Addition of cuprous chloride to the Grignard reagent provides the 1,6-addition product (29) in 40% yield in the case of the 1,4,6,9(1 l)-tetraene-3-ketone (28). The configuration of the 7-methyl group in (29) has not been established. ... 

Methoxy-cis-19-norpregna-l,3,5(10),17(20)-tetraene A solution of 31 g (109 mmolesi of estrone methyl ether in 600 ml of benzene is added rapidly to a solution of 469 mmoles of ethylidenetriphenylphosphorane in 1.2 liters of DMSO. After heating under nitrogen at 60° overnight, the reaction is cooled, poured into ice water, and extracted with three portions of hexane, backwashed with three portions of water and the hexane removed. The crude product, dissolved in petroleum ether (bp, 30-60°), is filtered through 225 g of alumina (activity I). The residue from the eluate consists of 95 % cis- and 5 % tran5-isomers, as determined by vpc analysis. After recrystallization from ether-methanol, 26.3 g (82%) of cw-isomer is obtained mp 76.5-77.5° [a]o 60°. 

R c-3-methoxy-l 8-methyl-17a-ethynylestra-l,3,5(10)-trien-17 -ol, 73 3-Methoxy-D-norestra-l,3,5( 10) -trien-16/3-carboxylic acid, 442 3-Methoxy-m-19-norpregna-l,3,5 (10), 17(20)-tetraene, 132 3-Methoxy-19-nor-17a-pregna-l, 3,5 (10), 15-tetraen-20-yn-17/3-01, 139... 

Katritzky et al. have studied, using pK measurements, the tautomerism of aza[10]annulenone (2-azabicyclo[4.4.1]undeca-4,6,8,10-tetraen-3-one) 68 (93H2483). Comparison of the pX s of 68 and of model compounds 69 and 70 suggests that 68a is the dominant tautomer pKr = -0.70).Tliis implies a significantly diminished preference for the oxy form in compound 68 compared to 2-pyridone pKr = -3.0). This result indicated that aza[10]-annulenones 68a and 70 should be viewed as 677-homoaromatic species. NMR spectra support this conclusion (93H2483). 

An example is the synthesis of substituted [2.2]paracyclophanes as reported by Hopfet al When hexa-l,2,4,5-tetraene 23 is treated with dimethyl acetylenedi-carboxylate 24 (an electron-poor acetylenic dienophile), the initially formed reactive intermediate 25 dimerizes to yield the [2.2]paracyclophane 26 ... 

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