Heteroatom directed photoarylation. Stereochemistry of aryloxyenone photocyclization

Abstract

Die Photolyse der Aryloxy‐enone (Ia), (Ib) und (II) wird untersucht.

Photocyclization reactions of substituted 2,2'-divinylbiphenyl derivatives

“…In contrast to the photochemistry of 19, where only one dihydrophenanthrene was observed, irradiation of 2-[o-(lphenylvinyl)phenyl]benzophenone (21) in benzene with 365-nm light furnished a mixture of two isomeric ketones [22 (60%) and 23 (20%)]. The structures of these two products were assigned as 4-benzoyl-9-phenyl- (22) and 9-benzoyl-9phenyl-9,10-dihydrophenanthrene (23) on the basis of their analytical and spectroscopic data (see Experimental Section for details). Structure 23 was further verified by a photochemical degradation.…”

“…24 Irradiation of 2-[o-(1 -Phenylvinyl)phenyl]benzophenone. A solution containing 140 mg of 21 in 275 mL of benzene was irradiated through a Vycor filter sleeve for 22 h. Removal of the solvent followed by thick-layer chromatography using a 20% ether-pentane mixture gave 9-phenylphenanthrene (17) (16 mg (10%) and 4-benzoyl-9phenyl-9,10-dihydrophenanthrene (22) [85 mg (60%)]: mp [116][117] °C; IR (KBr) The irradiation of 21 was also carried out with wavelength of light >365 nm. A 300-mg sample of 21 in 410 mL of benzene was irradiated through a uranium glass filter for 60 h. Removal of the solvent followed by chromatography on a 2 X 40 cm silica gel column using a 20% ether-pentane mixture gave 185 mg of 4-benzoyl-9-phenyl-9,10dihydrophenanthrene ( 22) as well as 60 mg (20%) of 9-benzoyl-9phenyl-9,10-dihydrophenanthrene ( 23): mp 147-148 °C; IR (KBr) The ratio of 22 and 23 did not change when the irradiation of 21 was carried out in the presence of 1-dodecanethiol.…”

“…14 Somewhat related nonoxidative cyclizations have also received wide attention in recent years from both the preparative and mechanistic points of view. [15][16][17][18][19][20][21][22] As part of a general study deeding with intramolecular [2 + 2]-cycloaddition and 6ir-electrocyclic reactions, we recently investigated the excited state behavior of several 2,2'-divinylbiphenyl derivatives. 15 During the course of these studies we found that the resulting photochemistry depends not only on the experimental conditions used, but also on the choice of the substituent groups attached to the double bond.…”

Probes for Narcotic Receptor-Mediated Phenomena. 33.1 Construction of a Strained trans-5,6-Ring System by Displacement of a Nitro-Activated Aromatic Fluorine. Synthesis of the Penultimate Oxide-Bridged Phenylmorphans

“…), although these conditions normally furnished a mixture of products. However, exclusive formation of trans -dihydrofurans was observed with certain fused-ring aryloxyenones. , Further, irradiation of the same type of substrates in protic solvents produced exclusively the less strained cis isomer in excellent yields. ,, This heteroatom-directed photoarylation protocol was unsuccessfully attempted for the synthesis of the cis tetracyclic b-isomer of the oxide-bridged 5-phenylmorphan in our laboratory. , In addition to the photochemical approach, the only other reported synthetic pathway 12 to the simple trans tricyclic hexahydrodibenzofurans involved constructing the furan ring prior to six-membered ring formation so as to establish the desired trans geometry at the 5,6-ring junction. However, extension of this route to the synthesis of our target molecules would require incorporation of suitable functionality at C 4a and C 1 to build the piperidine ring, which might prove extremely challenging in terms of both stereochemical control and compatibility of functionality.…”

Carbonyl transposition studies

“…Furthermore, a high degree of stereochemical control is possible (e.g., at C(2) and C(3) in C),2 and an important application of the photoreaction is the bonding of an aromatic ring to an angular carbon atom located at a ring junction. 3 Early in our studies, we discovered that while simple aryl vinyl ethers undergo inefficient photocyclization, excellent chemical and photochemical cyclization yields are obtained with 2-aryloxyenones (A, X = oxygen). The carbonyl group in A establishes a chromophore (enone), with which relatively low energy Pyrex-filtered light may be employed and at the same time presumably provides for stabilization of the intermediate ylide B as shown.…”