An efficient, mild and solvent-free synthesis of benzene ring acylated harmalines.

A facile synthesis of a series of benzene ring acylated analogues of harmaline has been achieved by Friedel-Crafts acylation under solvent-free conditions at room temperature using acyl halides/acid anhydrides and AlCl3. The reaction afforded 10- and 12-acyl analogues of harmaline in good yield, along with minor quantities of N-acyl-tryptamines and 8-acyl analogues of N-acyltryptamines.

Bis(4-nitro-phen-yl) 1,3-phenyl-ene-dimethyl-ene dicarbonate.

In the title mol-ecule, C(22)H(16)N(2)O(10), the dihedral angles between the benzene rings of the 4-nitro-phenyl groups and the central benzene ring are 32.7 (1) and 34.7 (1)°, while the dihedral angle between the two benzene rings of the 4-nitro-phenyl groups is 3.6 (2)°. In the crystal structure, weak inter-molecular C-H⋯O hydrogen bonds link mol-ecules into centrosymmetric dimers.

2,5-Dimethyl-hexane-2,5-diyl bis-(4-nitro-phen-yl) dicarbonate.

The title structure, C(22)H(24)N(2)O(10), contains two independent centrosymmetric mol-ecules. The only significant difference between the mol-ecules is the dihedral angle between the unique carbonate group (-O-CO(2)-) and the benzene ring, the values being 77.35 (8) and 66.42 (8)°. The crystal structure is stabilized by weak inter-molecular C-H⋯O hydrogen bonds.

trans-Cyclo-hex-2-ene-1,4-diyl bis-(4-nitro-phen-yl) dicarbonate.

Although the title mol-ecule, C(20)H(16)N(2)O(10), does not possess mol-ecular inversion symmetry, it lies on a crystallographic inversion centre which imposes disorder on the central cyclo-hexene ring. In addition, the cyclo-hexene ring has non-symmetry-related disorder over two sites, with the ratio of the major and minor components being 0.54:0.46. The overall effect is to produce four disorder components for the atoms of the cyclo-hexene ring. The side chain is perfectly ordered and the dihedral angle between the atoms of the carbonate group (O=CO(2)-) and the benzene ring is 72.99 (6)°.

trans-Cyclo-hexane-1,4-diyl bis-(4-nitro-phen-yl) dicarbonate.

In the title crystal structure, C(20)H(18)N(2)O(10), there are two independent mol-ecules, both of which lie on crystallographic inversion centres. In one mol-ecule the 4-nitro-phenyl dicarbonate groups are substituted in equatorial (A(eq)) positions of the chair-form cyclo-hexane ring while in the other mol-ecule the substitution is axial (B(ax)). The dihedral angles between the atoms of the symmetry-unique carbonate group (O=CO(2)-) and benzene ring for each mol-ecule are 47.3 (1)° for A(eq) and 11.7 (2)° for B(ax). In B(ax), this facilitates the formation of a weak intra-molecular C-H⋯O hydrogen bond, while the packing is stabilized by weak inter-molecular C-H⋯O inter-actions.