Simple 1,3-dienes undergo highly stereoselective hetero-Diels-Alder additions with SO2 at low temperature giving sultines. These reactions that are faster than the more exothermic cheletropic additions of SO2-producing sulfolenes. This has led to the invention of a new C-C bond-forming reaction combining electron-rich dienes and alkenes with SO2. The reaction cascade has been exploited to develop combinatorial, one-pot, four-component syntheses of polyfunctional sulfones, sulfonamides, and sulfonic esters. It also allows us to generate, in one-pot operations, enantiomerically enriched polypropionate fragments containing up to three contiguous stereogenic centers and a (E)-alkene unit. These fragments can be used directly in further C-C bond-forming reactions, such as cross-aldol condensations, thus permitting the expeditious construction of complicated natural products of biological interest (e.g., Baconipyrones, Rifamycin S, Apoptolidinone) and analogues. New ene reactions of SO2 have also been discovered; they open new avenues to organic synthesis.

The isolation and structural characterization of metallacyclic allyl (2a) and crotyl (2b) iridium complexes are reported. Complexes 2a and 2b are rare examples of iriduim allyl complexes that undergo nucleophilic attack at terminal position, rather than the central position, of the allyl unit. Structures of 2a and 2b were obtained by X-ray diffraction. Nucleophilic attack was observed at the carbon that is bound to iridium trans to phosphorus through a longer Ir-C bond. However, the effect of the trans phosphine ligand on the Ir-C bond lengths was smaller than the effect of the substituent on the allyl group in 2b. The competence of complexes 2a and 2b to be intermediates in the catalytic asymmetric allylic substitutions was evaluated by studying their reactivity towards stabilized carbon and heteroatom nucleophiles and comparing the rates and selectivities to those of the catalytic reactions. The stereoselectivity and regioselectivity of stoichiometric reactions of 2b were similar to those of reactions catalyzed by the previously reported iridium catalysts, supporting their intermediacy in the catalytic reactions. Based on the structural data, a model is proposed for the origin of stereoselectivity in iridium-catalyzed asymmetric allylic substitution reactions.

Table of ContentsGeneralExperimental Methods S2 Monitoring of Catalytic Reactions S3 Preparation of [Ir(COD)(P,C-L1)(ethylene)] (5) S3 Spectral data for [Ir(COD)(P,C-L1)(ethylene)] (5) S5 Preparation of [Ir(COD)(P,C-L1)(4)] (3) S8 Generation of Allylamine Complex 3 by Reaction of Allyl Amine 4 with the Combination of [Ir(COD)(P,C-L1)(L1)] and [Ir(COD)Cl] 2 and its Reaction with L1 and Ethylene S8 Spectral Data for [Ir(COD)(P,C-L1)(4)] (3) S9 Comparison of Catalysts S12 Measurement of Equilibrium Constants inTable 1 S16 Derivation of Kinetic Equations S17 Kinetic Measurements S18 References S22 S2General Methods. Elemental Analyses were performed by Robertson Microlit Laboratories, Inc. (Madison, NJ). GC/MS analyses were performed on an Agilent 6890N GC equipped with a 5973 MS and an HP-5ms column (30 m x 0.25 mm ID x 0.25 µm film). GC analyses were obtained on an Agilent 6890 GC equipped with an HP-5 column (25 m x 0.20 mm ID x 0.33 µm film) and an FID detector. NMR spectra were acquired on 500 MHz Varian Unity or Innova instruments. Chemical shifts are reported in ppm, relative to the solvent resonance (CDCl 3 = 7.26 ppm for 1 H, 77.0 ppm for 13 C) or to an external standard (CFCl 3 = 0 for 19 F and 85% H 3 PO 4 = 0 for 31 P). Coupling constants are given in hertz. HPLC analyses were carried out on a Waters chromatography system (1525 binary pump, 717+ autosampler, 2487 dual wavelength detector). Supercritical fluid chromatography analyses were carried out on a Berger ASC-1000 instrument with a single wavelength detector (λ= 220 nm) using a chiral solid phase column.Chromatography was conducted on Silicycle Siala-P Silica gel using hexanes/ethyl acetate, hexanes/ether, or pentane/ether mixtures. While many products were visible on TLC via UV, all products were identified by staining with KMnO 4 (orange).Reaction progress was monitored by GC and GC/MS with dodecane as the internal standard (10 µL). Branched-to-linear ratios were determined by 1 H NMR (usually the olefin protons) and GC/MS analysis in all cases except for the determination of the branched-to-linear ratio of 3b (NMR only), 3j (GC only), and 3c, 3e, and 3f (GC/MS only). Results from GC/MS and NMR spectroscopy were within 5-10% of each other in all cases.All starting materials were purchased from Aldrich, except for IrCl 3 , which was purchased from Pressure Chemical or obtained as a gift from Johnson-Matthey. Propylamine was stored over KOH. THF, pentane, benzene, ether, toluene, and CH 2 Cl 2 were purified by passing the degassed solvent (Ar) through a column of activated alumina (Solvent purification system purchased from Innovative Technologies of Newburyport, MA). (-)-N-(1phenylallyl)benzenamine, (-)-N-(hex-1-en-3-yl)benzenamine, (+)-N-(1-phenylallyl)benzenamine, [Ir(COD)(P,C-L1)(L1)] and [Ir(COD)(P,C-L1)Cl] were prepared by published methods. 1 . The branched to linear ratios of the allyl amines were higher than 97/3, and the ee's were higher than 96%.Benzene-d 6 and toluene-d 8 were degassed and dried over sodium and benzophenone. Kinetic data...