Dimers of 3,7-dehydrotropones (bicyclo[3.2.0]hepta-1(7),2,4-trien-6-ones)

2-(tert-Butyl)-3,7-dehydrotropone (7-(tert-butyl)bicyclo[3.2.0]hepta-1(7),2,4-trien-6-one; 1 ) was found to dimerize reversibly to 2A by [2 + 4]-cycloaddition/cycloreversion reaction. The equilibrium lies on the side of the highly strained dimer 2A in the solid state, and on the side of the monomer 1 in solution. The [2 + 4]-reaction is fully perisite-, regio- and stereoselective. Above room temperature, 1 irreversibly formed a decarbonylated dimer 6 , probably via the intermediate 9A or 9B , which resulted either from a dimerisation of 1 by [4 + 6]-cycloaddition or from a sigmatropic rearrangement of the originally formed dimer 2A or 2B . Similary, the 6-bromo derivative 14 afforded the corresponding decarbonylated dimer 15 . Should the formation of 6 and 15 be due to a primary cycloaddition then that reaction is fully peri-, site- and regioselective. Mild LiAlH₄-reduction of 6 and subsequent acetylation yielded the acetate 11 , the structure of which was established by an X-ray analysis. More vigorous LiAlH₄-treatment also reduced the terminal fulvenoid double bond of 6 and acetylation of the crude product led to the acetated 12 and 13 .     

A Facile Synthesis of Bicyclo[4.2.0]octa-1,3,5-trien-3-ol

Bicyclo[4.2.0]octa-1,3,5-trien-3-ol (2) has been synthesized in good yield via a Baeyer-Villiger reaction of the corresponding aldehyde 5 with permonophosphoric acid.     

Crystal and molecular structure of 9-exo-(4-nitrophenyl)thio-10endo-chlorotricyclo[6.3.1.02,7]dodeca-2(7),3,5-triene

Crystal and molecular structure of 9-exo-(4-nitrophenyl)thio-10-endo-chlorotricyclo[6.3.1.0^2,7]dodeca-2(7),3,5-triene (I) was determined by X-ray diffraction analysis: space group P2₁/c, a=9.514(1), b=13.457(1), c=13.163(2) Å, β=104.72(1)°, Z=4, R=0.041 (CAD-4 automatic diffractometer, λCuK_α, 2747 independent reflections with I≥3σ). The framework of molecule I consists of three condensed rings: the benzene ring, the cyclopentene ring having an envelope conformation with a flap at the bridging C atom, and the cyclohexane ring having a distorted chair conformation. The-SAr and Cl substituents have a trans-diaxial orientation at the cyclohexane ring. Molecule I is sterically hindered; it has appreciably reduced interatomic contacts: Cl…C₂, Cl…C₇, S…C₁₂, etc.     

The Synthesis of 12-Methyl-1, 2, 3, 4, 6, 7, 12, 12B-Octahydroindolo [2,3-A]Quinolizine (1), 1-Benzoyl-1, 2, 3, 4, 6, 7, 12, 12B-Octahydroindolo[2, 3-A]Quinolizine (2), and 1-Phenylcarbinol-1, 2, 3, 4, 6, 7, 12, 12B-Octahydroindolo[2, 3-A]Quinolizine (3)

12-Methyl-l, 2, 3, 4, 6, 7, 12, 12b-octahydroindolo[2, 3-a]quinolizine (1) is synthesized through a new route developed in our laboratory. The most important step in this synthesis is the condensation of I-methyltryptophyl bromide (4) with 2-piperidone (5) to give N -(2-(1-methylidol)-3-ylethyl)-2-piperidone (6) in good yield (70%). The synthesis of 1-benzoyl-1, 2, 3, 4, 6, 7, 12, 12b-octahydroindolo(2, 3-a]quinolizine (2) and 1-phenylcarbinol-1, 2, 3, 4, 6, 7, 12, 12b-octahydroindolo[2, 3-a]quinolizine (3) follow the method developed by Wenkert. But the yield of tetrahydropyridine 9 from partial hydrogenation of pyridinum bromide 8 with 10% palladium-charcoal is 84% which is much higher than the best yield (40%) in the literature, since the phenyl group contribute additional stability.