Cycloocta-2,4-dien-l-one

Irradiation of cycloocta-2,4-dien-l-one (55) in pentane gives a racemic photodimer, anti-tricyclofSAO.O Jhexadeca- , 11 -diene-3,16-dione (60) in 10% yield along with polymeric materials 34). Efficient and enantioselective photodimerization of 58 was achieved by irradiation of the 2 1 inclusion complex 59 formed between 2 a and 5813). When a solution of 2a and an equimolar amount of 58 in ether-hexane (1 1) was kept at room temperature for 12 h, 59 was obtained as colorless needles of mp 105 to 108 °C. Irradiation of 59 in the solid state for 48 h gave (—)-60 of 78 % ee in 55 % yield. 

Keywords cycloocta-2,4,6-trien-l-one, cycloocta-2,4-dien-l-one, inclusion complex, [2+2] photocycloaddition, cyclobutane... 

Cycloocta-2,4-dien-l-one (95) exists as an equilibrium mixture of the conformers 95a and 95b in solution, and conversion between these two enantiomeric forms is too fast to allow their isolation at room temperature. Photoreaction of 95 in pentane for 1 hr gives racemic 96 in 10% yield along with polymers. When a solution of (—)-ll and 95 was kept at room temperature for 12 h, a 3 2 inclusion complex of (—)-ll with 95a was obtained as colorless needles. Irradiation of the 3 2 complex of (—)-ll with 95a for 48 hr gave (—)-96 of 78% ee in 55% yield. X-ray crystal structure analysis is given in Ref. 51. 

Irradiation of the 2 1 host-guest crystals of cyclohex-2-enone 81 with the axle-wheel-type host compound (— )-5 as an aqueous suspension caused regio- and enantioselective [2 + 2] photodimerization to afford the (— )-anti-head-to-head dimer 82 of 48% ee in 75% chemical yield (Scheme 18) [86]. Similarly, solid-state photolysis of the 3 2 complex of cycloocta-2,4-dien-l-one 83 with (R,R)-( — )-4 gave the (-)-anti-head-to-head dimer 84 in moderate optical yield [87]. 

Photoreaction of Tropolone Alkyl Ether, Cycloocta-2,4-dien-l-one and Pyridone... 

Irradiation of the 1 2 inclusion complex of cycloocta-2,4-dien-l-one (108) with 10 for 48 h gave (-)-109 of 78% ee in 55% yield [65]. The mechanism of this enantioselective reaction has been studied by X-ray analysis of the inclusion complex [66]. 

Ring closure to cyclobutanes via valence isomerization of cycloocta-l,3,5-trienes is also possible when carbonyl functions are present in the ethane fragment. Thus, reaction of cyclohepta-2,4,6-trienone (tropone) with diazopropane gives 8,8-dimethylcycloocta-2,4,6-trienone (16, R = H), which rearranges quantitatively to 8,8-dimethylbicyclo[4.2.0]octa-2,4-dien-7-one (17, R = H).67... 

Addition of (Z,Z)-cycloocta-l,4-diene to one equivalent of iodine and two equivalents of sil-ver(I) perchlorate in methanol, gave fra x-2,6-dimethoxybicyclo[5.1.0]octane (4) in 57% yield. Reaction of the dibromocyclooctane 2 with silver(I) perchlorate in methanol also gave the diether 4 in 56% yield. ... 

The complex functions as the most suitable source of the tricarbonylruth-enium unit in syntheses of tiicarbonyl(i -diene)ruthenium complexes. Derivatives of 1,3-cyclohexadiene, 1,3-cycloheptadiene, cycloheptatriene, cycloocta-tetraene, 2,4,6-cycloheptatrien-l-one, bicyclo[3.2.1]octa-2,6-diene, bicyclo-[3.2.1]octa-2,4-diene, and butadiene have been prepared by displacement of 1,5-cyclooctadiene. 

Chiral (E)-enolethers. A degassed soln. of (5R)-5-cyclohexyl-2-ethenyl-l,3-dioxolan-4-one (2 1 cisjtrans) in THF added to ca. 1 eq. of a suspension of bis(l,5-cycloocta-diene)nickel(0) in the same solvent under N2, stirred until the complex dissolved (10 min), after 3h the resulting rust-coloured precipitate collected, suspended in methylene chloride, treated with MejSiCl, and stirred for 30 min intermediate 7c-allylnickel complex (Y 78%), in benzene treated with DMF and 5 eqs. 1-iodo-propane, irradiated with a sunlamp (GE 275 W Model RSW) for 2,5 h at 10°, stirred for a further 3 h, diluted with pentane to precipitate nickel halide, and stirred for a further 4 h product (Y 82% E/Z 9 1). Subsequent treatment with acetals afforded 2-p-alkoxy-l,3-dioxolan-4-ones with asym. induction, thereby providing an alternative to asym. aldol condensation. F.e. inch reaction with ar. and a,P-ethylene-bromides s. D.J. Krysan, P.B. Mackenzie, J. Am. Chem. Soc. 110, 6273 (1988). 

Various reactions have been described in which the transition metal has become part of a cyclic system ( metallacycles ) on reaction with the double bond of methylenecyclopropane. (2,2 -Bipyridine)(cycloocta-l,5-diene)nickel reacted with an excess of methylenecyclopropane to give 8-(2,2 -bipyridyl)-8-nickeladispiro[2.1.2.2.]nonane (4) in excellent yield.When this nickel compound was treated with carbon monoxide, dispiro[2.1.2.2.]nonan-8-one (5) was obtained in 50% yield. ... 

When (2,2 -bipyridine)(cycloocta-l,5-diene)nickel was used as the catalyst various isomeric (2,2 -bipyridyl)nickelaspirocycloalkanes 4 and 5a-c were isolated.As expected, treatment of the dispiro complex 4 with methyl acrylate or maleic anhydride released dispiro[2.1.2.1]oc-tane (1) whereas the complexes 5 with one cyclopropane ring opened gave mainly 5-methyl-enespiroheptane 2. The formation of the 4-methylene isomer (from 5c) has not been observed in the dimerization reaction with other nickel(O) complexes. A few more nickel(O) complexes with an ability to catalyze the oligomerization of methylenecyclopropane have been de-scribed. ... 

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