Bicyclic thiaspiro[4.n]alkanones: Investigating their total stereochemistry achieved by the catalyst-free sulfa-Michael reaction

A series of twenty-two examples of bicyclic 1-aryl-4-hydroxy-2-thiaspiro[4.n]alkanones ( 3, 4 ), where aryl = phenyl, 4-CH 3 OC 6 H 4 , 4-NO 2 C 6 H 4 , 4-FC 6 H 4 , 4-ClC 6 H 4 , 4-CH 3 C 6 H 4 ,1-naphthyl, 4-N(CH 3 ) 2 C 6 H 4 , and n = 4, 5 were obtained from a catalyst-free sulfa-Michael reaction in refluxing ethanol as a solvent at up to 98% of yield, starting from the readily available 2-arylidene-cycloalkanones ( 1) and 1,4-dithian-2,5-diol ( 2 ) as the precursors. Vinyl ketones 1 were synthesized by reacting simple cyclopentanone and cyclohexanone with aryl aldehydes through well-established procedures. Subsequently, effort s were devoted to isolation, structural characterization by NMR and SC-XRD techniques, and configuration assignment to identify diastereomers containing multiple chiral centers at the bicyclic scaffolds ( 3, 4 ), which were presented, discussed, and compared to precedent studies for 1-tetralone and 1-indanone analogues. (c) 2022 Elsevier B.V. All rights reserved.