Albert C. Pratt

Quinoline synthesis: scope and regiochemistry of photocyclisation of substituted benzylidenecyclopentanone O-alkyl and O-acetyloximes

Irradiation of substituted 2-benzylidenecyclopentanone O-alkyl and O-acetyloximes in methanol provides a convenient synthesis of alkyl, alkoxy, hydroxy, acetoxy, amino, dimethylamino and benzo substituted annulated quinolines. para-Substituents yield 6-substituted-2,3-dihydro-1H-cyclopenta[b]quinolines with 8-substituted products being obtained from ortho-substituted starting materials. Reactions of meta-substituted precursors are highly regioselective, with alkyl substituents leading to 5-substituted 2,3-dihydro-1H-cyclopenta[b]quinolines and more strongly electron-donating substituents generally resulting in 7-substituted products. 2-Furylmethylene and 2-thienylmethylene analogues yield annulated furo- and thieno-[2,3e]pyridines respectively. Sequential E- to Z-benzylidene group isomerisation and six pi-electron cyclisation steps result in formation of a short-lived dihydroquinoline intermediate which spontaneously aromatises by elimination of an alcohol or acetic acid. For 2-benzylidenecyclopentanone O-allyloxime, singlet excited states are involved in both steps.

Benzyl­ammonium 2,4‐bis­(di­cyano­methyl­ene)‐2,3‐di­hydro­isoindolide

The cation and anion of the title salt, C7H10N+.C14H4N5−, are both bisected by a crystallographic mirror plane. Extensive hydrogen bonding, with the R66(28) graph-set motif, connects the ions into layers.

The (1RS,2RS,7RS,8RS)- and (1RS,2SR,7SR,8RS)-diastereoisomers of 8,9,11,12-tetra­chloro-N-ethyl­tricyclo­[6.2.2.02,7]dodeca-9,11-diene-1,10-dicarboximide

Two racemic diastereoisomers, C16H15Cl4NO2, of the title 1,4-photoadduct of N-ethyltetrachlorophthalimide with cyclohexene have been isolated and their stereostructures determined.

2,2′-[2,3-Di­hydro-2-(prop-2-enyl)-1H-isoindole-1,3-diyl­idene]bis(propane­di­nitrile)–tetra­thia­fulvalene (1/1), TCPI–TTF

The title complex, C17H9N5*C6H4S4, contains pi-deficient bis(dinitrile) and TTF molecules stacked alternately in columns along the a-axis direction; the interplanar angle between the TTF molecule and the isoindolinyl C4N[C(CN)2]2 moiety is 1.21 (4) degrees. The N-allyl moiety in the TCPI molecule is oriented at an angle of 87.10 (10) degrees with respect to the five-membered C4N ring, and the four C[triple-bond]N bond lengths range from 1.134 (3) to 1.142 (3) A, with C-C[triple-bond]N angles in the range 174.3 (3)-176.9 (2) degrees. In the TTF system, the S-C bond lengths are 1.726 (3)-1.740 (3) and 1.751 (2)-1.763 (2) A for the external S-C(H) and internal S-C(S) bonds, respectively.

Photoinduced benzylation of 1,4-dimethoxynaphthalene by benzyl halides

Irradiation of 1,4-dimethoxynaphthalene (DMNH) in the presence of 4-substituted benzyl chlorides (X–C6H4CH2Cl, X = H, Cl, CN OR NO2) in either acetonitrile or benezene solution results in benzylation of DMNH, predominantly at position 2 and to a lesser extent on the unsubstitued ring. Steady-state and flash photolysis studies show that charge transfer between singlet excited DMNH and the chlorides is involved. The reaction occurs predominantly in-cage via concerted electron transfer and carbon-chlorine bond cleavage with X = H or Cl, while with X = NO2 fragmentation of the benzyl chloride radical anion occurs out-of-cage, but the process in this case is much less efficient due to competing back electron transfer.