Synthese von Thiacycloocteno-1,2,3-selenadiazolen/Synthesis of Thiacycloocteno-1,2,3-selenadiazoles

Abstract

The isomeric thiacyclooctanones 1b-d are transformed via the semicarbazones Z-2b,c, E-2b,c and 2d to the bicyclic 1,2,3-selenadiazoles 3b,c, 3b´,c´ and 3d. The ring closure reaction with SeO2 is highly regioselective and doesn’t depend on the Z /E -ratio of the semicarbazones. A detailed 1H and 13C NMR study was made for 1, 2 and 3.

Product Class 27: Selenazoles and Tellurazoles Containing One or More Other Heteroatoms

“…[22][23][24] This last aspect has been of particular interest in the context of strained cycloalkynes and the selenadiazole method has allowed access to cyclooctyne, [25] cycloheptyne, cyclohexyne, and cyclopentyne, [26] 3-thiacyclooctyne, [27,28] E-cycloundec-1-en-3yne, [29] cyclodeca-1,6-diyne, [30] 9-oxabicyclo[6.1.0]non-2-yne and 9-oxabicyclo[6.1.0]non-3yne, [31] 4-oxacyclooctyne, [32] a range of C 9 -C 12 cycloalkadiynes, [33] and 4-and 5-hydroxycyclooctyne. [22][23][24] This last aspect has been of particular interest in the context of strained cycloalkynes and the selenadiazole method has allowed access to cyclooctyne, [25] cycloheptyne, cyclohexyne, and cyclopentyne, [26] 3-thiacyclooctyne, [27,28] E-cycloundec-1-en-3yne, [29] cyclodeca-1,6-diyne, [30] 9-oxabicyclo[6.1.0]non-2-yne and 9-oxabicyclo[6.1.0]non-3yne, [31] 4-oxacyclooctyne, [32] a range of C 9 -C 12 cycloalkadiynes, [33] and 4-and 5-hydroxycyclooctyne.…”

“…[37,38] The synthesis of 1,2,3-selenadiazoles by reaction of semicarbazones with selenium dioxide in acetic acid was the original method introduced in 1970, [22][23][24] and has since been widely applied to synthesis of 4-aryl-, [36] 4-arylalkyl-, [39] 4-styryl-, [40] 4-cyclopropylsulfonyland 4-pyrazolylsulfonyl-, [41] 5-arylsulfonyl-, [35,37,42] 5-carbamoyl-, [43] cycloalkene-fused, [44,45] phenanthro-fused, [46] steroid-substituted, [47] and bis-1,2,3-selenadiazoles. [25][26][27][28][29][30][31][32][33][34] Since the target selenadiazoles are designed to undergo ready extrusion of selenium and nitrogen, they are somewhat unstable and care must be taken to use mild conditions in their preparation. [24] Scheme 25 Synthesis of 1,2,3-Selenadiazoles in Acetic Acid [24] (48); Typical Procedure: [24] To a stirred suspension of acetaldehyde semicarbazone (65 g, 0.64 mol) in AcOH (500 mL) at rt was gradually added finely powdered SeO 2 (71 g, 0.65 mol).…”