Syntheses of some 3-substituted isothiochromen-1-ones

Base-promoted thioannulation of o-alkynyl oxime ethers with sodium sulfide for the general synthesis of isothiocoumarins

A general and efficient strategy for the one-pot synthesis of isothiocoumarin-1-ones has been developed via the base-promoted 6-endo-dig thioannulation of o-alkynyl oxime ethers using the cheap and readily available Na₂S as the sulfur source. Mechanistic studies disclosed that the reaction proceeded through two C-S bond formations, N-O bond cleavage and the final hydrolysis of imines.

Crystal structures of two new isocoumarin derivatives: 8-amino-6-methyl-3,4-diphenyl-1H-isochromen-1-one and 8-amino-3,4-diethyl-6-methyl-1H-isochromen-1-one

The title compounds, 8-amino-6-methyl-3,4-diphenyl-1H-isochromen-1-one, C22H17NO2, (I), and 8-amino-3,4-diethyl-6-methyl-1H-isochromen-1-one, C14H17NO2, (II), are new isocoumarin derivatives in which the isochromene ring systems are planar. Compound II crystallizes with two independent mol-ecules (A and B) in the asymmetric unit. In I, the two phenyl rings are inclined to each other by 56.41 (7)° and to the mean plane of the 1H-isochromene ring system by 67.64 (6) and 44.92 (6)°. In both compounds, there is an intra-molecular N-H⋯O hydrogen bond present forming an S(6) ring motif. In the crystal of I, mol-ecules are linked by N-H⋯π inter-actions, forming chains along the b-axis direction. A C-H⋯π inter-action links the chains to form layers parallel to (100). The layers are then linked by a second C-H⋯π inter-action, forming a three-dimensional structure. In the crystal of II, the two independent mol-ecules (A and B) are linked by N-H⋯O hydrogen bonds, forming -A-B-A-B- chains along the [101] direction. The chains are linked into ribbons by C-H⋯π inter-actions involving inversion-related A mol-ecules. The latter are linked by offset π-π inter-actions [inter-centroid distances vary from 3.506 (1) to 3.870 (2) Å], forming a three-dimensional structure.

3-tert-Butyl-1H-isochromene-1-thione

The title compound, C₁₃H₁₄OS, crystallizes with two independent mol­ecules in the asymmetric unit. The unit cell contains three voids of 197 ų, but the residual electron density (highest peak = 0.24 e Å⁻³ and deepest hole = −0.18 e Å⁻³) in the difference Fourier map suggests no solvent mol­ecule occupies this void. The crystal structure is stabilized by π–π inter­actions between the isocoumarin ring systems, with centroid–centroid distances of 3.6793 (14) and 3.6566 (15) Å.