Aromatic Allylsulfenylation with in Situ Generated Allylic Thiols under the Heck Conditions

Abstract

A wide structural variety of S-allylic thiocarbamates 2 can be prepared in good yields by the rearrangement of O-allylic thiocarbamates 1 under three different conditions: thermal activation (neat, 120—150 °C), palladium(0) (25—65 °C), and palladium(II) catalysis (25—65 °C). Of the two possible regioisomers of unsymmetrical S-allylic thiocarbamates 2, those of higher thermodynamic stability can be prepared in high purity under either thermal activation or palladium(0) catalysis. Although the thermodynamically less stable regioisomers of 2 are, in general, hard to be prepared in high purity, some of them (e.g., 2d and 2h′) can be obtained with an exclusive or high selectivity by the catalysis of palladium(II). The stereoisomeric pair of 2j and 2j′ can be prepared selectively by the palladium(0)-catalyzed rearrangement of 1j and 1k, respectively. These reactions proceed with retention of configuration at the allylic stereocenters. S-Allylic (2) and S-alkyl thiocarbamates (7) undergo fragmentation to generate thiolates in the presence of inorganic bases (e.g., K2CO3, K2CO3·Et4N+I−) by heating in an aprotic solvent; the thus-formed thiolates react with aromatic iodides and vinyl bromides in the presence of palladium(0) complexes to furnish aryl and vinyl sulfides, respectively. A wide variety of aryl sulfides can be prepared in good yields irrespective of the kind of substituents and their substitution positions (o-, m-, p-) under conditions B [Pd(OAc)2, PPh3, K2CO3·Et4N+I−, dioxane, 100 °C]. Under conditions E [Pd(OAc)2, PPh3, Cs2CO3, dioxane, 100 °C], better yields result specifically for the sulfenylation of aromatic iodides bearing substituents having large Hammett σ constants.

Iodine(V) Reagents in Organic Synthesis. Part 3. New Routes to Heterocyclic Compounds via o-Iodoxybenzoic Acid-Mediated Cyclizations: Generality, Scope, and Mechanism

“…Unfortunately, application of the present method to other substrates led to a mixture of products due to competitive [1,3]-sigmatropic rearrangement and lack of stereoselectivity in this process. These results are consistent with previous findings that secondary thiocarbamates give rise to mixtures of [1,3]- and [3,3]-sigmatropic rearrangement products 3 Thionocarbamates in the IBX-Mediated Cyclization

4 IBX-Mediated Synthesis of Cyclic Urethanes and cis -1,2-Amino Alcohols a a Reagents and conditions: (a) CAN (5.0 equiv), CH 3 CN:H 2 O (5:1), 25 °C, 20 min, 86%; (b) NaOH (10 equiv), EtOH, 75 °C, 1 h, 95%.

5 Synthesis of Aminosugar 69c a a Reagents and conditions: (a) p -MeOC 6 H 4 NCO (1.1 equiv), DBU (0.1 equiv), CH 2 Cl 2 , 25 °C, 1 h, 95%; (b) IBX (2.0 equiv), THF:DMSO (10:1), 90 °C (sealed tube), 8 h; then IBX (2.0 equiv), 8 h, 84%; (c) CAN (5.0 equiv), CH 3 CN:H 2 O (5:1), 0 °C, 30 min, 90%.

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New Facile One-Pot Synthesis of Isobutyl Thiocarbamate in Recycling Solvent Mixture

“…Methods for the alkyl thiocarbamate synthesis using reaction of alkyl dixanthates and amines in the presence of an oxidizing agent have been described [45]. In the Newman-Kwart rearrangement (intermolecular isomerization) of O-thiocarbamate, S-thiocarbamate is obtained, which is used as herbicides in plant protection [46][47][48][49].…”

Novel Model Sulfur Compounds as Mechanistic Probes for Enzymatic and Biomimetic Oxidations

“…CiP was kindly provided by Novo Nordisk. Sulfides 1c − d ,7 2 ,35 3 ,36 4 36,37 and 5 ,37 were obtained by standard procedures and exhibited physical properties identical to those reported in the literature. Diphenylmethyl phenyl sulfoxide,7 diphenylmethyl methyl sulfoxide ( 14 ),38 allyl phenyl sulfoxide,39 cinnamyl phenyl sulfoxide,40 diphenylmethyl phenyl sulfone,41 diphenylmethyl methyl sulfone,41a allyl phenyl sulfone,42 cinnamyl phenyl sulfone42,43 and cinnamyl methyl sulfone44 were prepared by oxidation (of the sulfide) with 1 or 3 equivalents of dimethyldioxirane,45 and exhibited physical properties identical to those reported in the literature.…”