Diastereoselective synthesis of cyclopentene spiro-rhodanines containing three contiguous stereocenters via phosphine-catalyzed [3 + 2] cycloaddition or one-pot sequential [3 + 2]/[3 + 2] cycloadditionElectronic supplementary information (ESI) available: General information, experimental procedures, characterized data and copies of 1H and 13C NMR spectra for products. CCDC 1494917. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6ra23399f

Two different diastereoselective phosphine-catalyzed cascade reactions to form cyclopentene spiro-rhodanine scaffolds are described. In the first approach, alkynoate derivatives and 5-arylidene-3-( tert -butyl)-2-thioxothiazolidin-4-one react in the presence of PBu 3 through a [3 + 2] cycloaddition to afford 5-spiro-cyclopentene-rhodanines in high yields (up to 99%) and with excellent diastereoselectivities [20 : 1 diastereomeric ratio (dr)]. In the second approach, the sequential [3 + 2]/[3 + 2] annulation reaction of ethyl 5-phenylpent-2-ynoate, substituted arylethylpropiolates, amines, and carbon disulfide with phosphine catalysis produces the corresponding monospirocyclic rhodanine products in good yields (up to 92%) and with excellent diastereoselectivities (up to 20 : 1 dr). 5-Spiro-cyclopentene-rhodanine derivatives have been synthesized through two different diastereoselective phosphine-catalyzed cascade reactions in excellent diastereoselectivities and good to excellent yields.