Irradiation, of bicyclo

It has been reported that irradiation of bicyclo[5.1.0]octa-3,5-dien-2-one (63) in methanol leads to a mixture of racemic tricyclo[4,2.0.03,5]oct-7-en-2-one (65), 37, and cyclohepta-l,3,5-triene35). Control of the reaction was also tried in expectation... 

Acetic anhydride, with 2-hep-tanone to give 3-n-butyl-2, 4-pentanedione, 51, 90 ACETIC FORMIC ANHYDRIDE, 50, 1 Acetone azine, 50, 2 ACETONE HYDRAZONE, 50, 2, 28 Acetophenone, 54, 93 as sensitizer for irradiation of bicyclo[2.2.1]hepta-2,5-diene to give quadricyclane,... 

Bicyclo[2.2.1]hept-7-yl cations, formed via the corresponding diazonium ions by diazotization of bicyclo[2.2.1]heptan-7-amine derivatives, rearrange partially to give bicyclo[3.2.0]heptanes (Houben-Weyl, Vol. 4/4, pp 106-107). Related diazonium ions can also be formed by irradiation of bicyclo[2.2.1]heptan-7-one tosylhydrazones in diluted sodium hydroxide and rearrange to form predominantly bicyclo[3.2.0]heptan-e. o-2-ols. On photolysis, the hydrazone 17 in 0.2 M sodium hydroxide gave t> <7o-2-methylbicyclo[3.2.0]heptan-exo-2-ol (18) with 77% selectivity and in 72-78% overall yield (GC).68... 

On ultraviolet irradiation of bicyclo[2.2.1]hept-5-en-2-one in diethyl ether for 1 hour, the rearrangement product bicyclo[3.2.0]hept-2-en-7-one (33) was formed in 90% yield.103 Other bicyclo[n.m.l]alkenones gave the rearranged cyclobutane products, albeit in lower... 

A direct entry to the quadricyclene series has been gained through photoisomerization of bicyclo [2.2.1 ]heptadienes. Bicyclo [2.2.1 ]hepta-dien-2,3-dicarboxylic acid (Formula 194), undergoes light-induced valence tautomerization to Formula 195 (75). The parent quadricyclene 196 has been prepared by direct irradiation of bicyclo [2.2. l]heptadiene... 

Direct irradiation of bicyclo[2.2.2]oct-5-en-2-one (11) in diethyl ether gave the 1,3-shift product, bicyclo[4.2.0]oct-4-en-7-one (12), which on further irradiation lost ketene without any detectable reverse 1,3-shift, to give eyclohexa-1,3-diene. On the other hand, acetone sensitized photolysis of bicyclo[2.2.2]oct-5-en-2-one (11) gave the 1,2-shift photoproduct, tricyclo[3.3.0.0 ]oc-tan-3-one (13), implicating a triplet excited state for this reaction and a singlet excited state for the 1,3-shift. ... 

Acetophenone sensitized irradiation of bicyclo[2.2.1]hepten-2-ones 27 affords tricyclo-[3.1.1.02,6]heptan-3-ones 28. 

Dihydrobiphenyls are formed on irradiation of bicyclo[2.2.2]octenediones. Extrusion of CO is the initial photochemical step. A CIDNP study has examined the photochemical reactions between l-acetylindole-2,3-dione and various hydrogen donors. ... 

Irradiation of the ketone (6) in argon-degassed cyclohexane brings about Norrish Type I fission. In this case decarbonylation does not result and the triplet biradical formed by the fission affords the aldehyde (7). The enol (8) is also a product of this irradiation. An aldehyde is also the principal product on irradiation of (9) in benzene. The a-fission affords the aldehyde derivative (10) in 90% yield. Analogous behaviour is observed on irradiation of bicyclo-heptanone (11) to afford an aldehyde that was a key intermediate in the synthesis of dimethyl secologanoside. ... 

When bicyclo I 3.1.01 hexanone and bicyclo 14.1.01 heptanone are substituted by electron-withdrawing groups at C(P) a ring-expanded product is formed. Similarly, the irradiation of bicyclo 15.1.01 octanone and bicyclolo.I.olnonanone in the presence of EtjN led to the ring-expanded products (Scheme 62). 

Convenient new routes to tricyclo[4,1,0,0 ]hept-3-ene and its derivatives have been disclosed. Acetone-sensitized irradiation of bicyclo[3,2,0]hept-6-en-2-one affords the ketone (624), whose enol phosphate is reduced by lithium-ammonia to give the parent alkene (625). " A second route is also described, starting from the 7,7-di-bromonorcarane derivatives (626) and (627). Reaction of (626) with methyl-lithium in ether at 0°C afforded a 3 1 mixture of the tricycloheptenes (628) and (629) similar reaction of (627) gave (630 40%), but reactions of the parent dibromide were unsuccessful. Catalytic Ag ion causes the rearrangement of (628) and (629) to, respectively, 3-methyl- and 1-methyl-cycloheptatriene. Initial Ag" attack at the least hindered edge bond is implicated. Attempted preparation of the tetrahedrane dimer (631) by the addition of dibromocarbene to homobenzvalene followed by treatment of the adduct so obtained with excess methyl-lithium in ether at 0°C afforded instead 5-ethynyl-cyclohexa-1,3-diene. 

Interratingly, irradiation for 6 h of the 1 1 complex 61 compc d of 8 a and 58 which had been prepared by keeping a solution of 8a and an equimolar amount of 58 in benzene-hexane at room temperature for 12 h (colorless needles of mp 133 to 136 °C) gave the optically active photocyclization product (—)-bk yclo[4.2.0]oct-7-en-2-one (62) Qa]p —60.6 (c 0.18, CHCI3)] in quantitative yield The photocyclization reaction is in contrast to the photodimerization of 58 in 59. In the case of 61, the photodimerization of 58 is probably prevented by steric hindrance. It is almost certain that one optical conformer of 58 is included in 61, but a real proof of this fact requires an X-ray structural study in the future. However, the formation of the optically active 62 is valuable, because photoreaction of 58 in solution does not give any intramolecular photocyclization product It has been reported that irradiation of bicyclo[5.1.0]octa-3,5-dien-2-one (63) in methanol leads to a mixture of racemic tricyclo[4.2.0.0 ]oct-7-en-2-one (65), 37, and cyclohepta-l,3,5-triene Control of the reaction was also tried in expectation... 

Fused Five-membered Rings.—Tricyclo[3.3.0.0 ]octan-3-ones (52) and (56) are readily obtained from the irradiation of bicyclo[2.2.2]octanones [e.g. (51)] or by the thermal decomposition of 2-cyclopenten-l-yldiazomethylketones (55)... 

ODPM product on sensitized irradiation in acetone. Similar results were obtained on direct irradiation of bicyclo[2.2.1]heptenones 105 and 107, which gave the 1,3-acyl migration products 106 and 108, respectively, in addition to the corresponding cyclopentadienes (Scheme Direct irradiation of... 

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