Synthesis and Crystal Structure Determination of Methyl 2-acetyl-5′-phenyl-2H-spiro[benzo[d]isothiazole-3,3′-pyrazole]-1,1-dioxide-2′(4′H)-carboxylate and Methyl 2-acetyl-5′-(2-thienyl)-2H-spiro[benzo[d]isothiazole-3,3′-pyrazole]-1,1-dioxide-2′(4′H)-carboxylate

Dilithiated C (α), N -carbomethoxyhydrazones were condensed with lithiated methyl 2-(aminosulfonyl)benzoate to afford intermediates that were isolated and not characterized but cyclized with acetic anhydride, which also resulted in N -acetylation. The X-ray crystal structure determinations of methyl 2-acetyl-5′-phenyl-2 H -spiro[benzo[ d ]isothiazole-3,3′-pyrazole]-1,1-dioxide-2′(4′ H )-carboxylate and methyl 2-acetyl-5′-(2-thienyl)-2 H -spiro[benzo[ d ]isothiazole-3,3′-pyrazole]-1,1-dioxide-2′(4′ H )-carboxylate products were a follow up for absorption spectra, and they confirmed their structures. Mechanistic intermediates to describe the reaction may include C -acylated intermediates that cyclize to spiro( N -benzoisothiazole dioxide-pyrazole) instead of N -carbomethoxypyrazole- ortho -benzenesulfonamides. Crystals of C 19 H 17 N 3 O 5 S 7 are monoclinic, P 2 1 / c , a = 11.899(2) Å, b = 17.562(4) Å, c = 9.484(2) Å, β = 111.03(3)°, Z = 4, V = 1849.9(6) Å 3 , R 1 = 0.0857 and wR 2 = 0.2216 for reflections with I > 2σ( I ); crystals of C 17 H 15 N 3 O 5 S 2 8 are orthorhombic, Pbca , a = 16.045(3) Å, b = 10.746(2) Å, c = 20.389(4) Å, Z = 8, V = 3516(1) Å 3 , R 1 = 0.0841 and wR 2 = 0.2179 for all reflections with I > 2σ( I ). Graphical Abstract X-ray crystal analysis was important for determining the conformation of the structure of N -acetyl- N ′-carbomethoxy-spiro(benzoisothiazole–pyrazole)dioxides prepared by the condensation and twofold cyclization of dilithiated C (α), N -carbomethoxyhydrazones and methyl 2-(aminosulfonyl)benzoate.