Download PDF
Synlett 2005(8): 1340-1341  
DOI: 10.1055/s-2005-865239
SPOTLIGHT
© Georg Thieme Verlag Stuttgart · New York

Sulfur Dioxide

Freddy Fonquerne*
EPFL/ISIC/LGSA, 1015 Lausanne-Dorigny, Switzerland
e-Mail: freddy.fonquerne@epfl.ch;

Dedicated to my father


Further Information

Publication History

Publication Date:
21 April 2005 (online)

 PDF Download Permissions and Reprints All articles of this category

Biographical Sketches

Freddy Fonquerne was born in 1978 in Briançon, France. He studied chemistry at the University Louis Pasteur of Strasbourg where he graduated from the European School of Chemistry, Polymers and Materials (ECPM) and obtained a Master’s degree. Then, he moved to Lausanne (Switzerland) where he is currently in the last year of his Ph.D. studies at the Ecole Polytechnique Fédérale de Lausanne (EPFL) under the supervision of Prof. Pierre Vogel. His area of research includes the Umpolung of dienes with sulfur ­dioxide and applications to natural product synthesis.

Introduction

Sulfur dioxide, obtained by burning sulfur in air, is a useful and suitable solvent and reagent for a large number of reactions. [1] [2] It has a broad liquid range (mp -75 °C and bp -10 °C), a comparably high solvation power for both ­ionic and covalent compounds, and low nucleophilicity. It is also a Lewis acid that is able to complex unsaturated ­organic compounds. Recently, this reagent has been used in the synthesis of long chain polyketides, [3] sulfones, ­sulfinates, sulfonamides, and methanesulfonic acid.

Abstracts

(A) Alkenes are isomerized by sulfur dioxide. The process is ­generally explained by invoking an ene reaction between an SO2 molecule and the alkene. [4] Recently, Vogel et al. revised this mechanism [5] and showed that polysulfones resulting from the co-polymerization of alkenes and SO2 catalyze the reaction. This has led to the development of a new method for the selective cleavage of methyl-substituted allyl ethers under neutral conditions. [6]

(B) Methane is transformed selectively to methanesulfonic acid at low temperature by liquid-phase sulfonation of methane with SO2 and O2 in the presence of Pd salts and Cu salts [7] as the catalysts or of CaO as promoter. [8]

(C) Irradiation of N-hydroxy-2-thiopyridone esters with visible light in the presence of sulfur dioxide gives the corresponding thiosulfonates. These can be converted into sulfones by treatment with KOH and an alkylating agent. [9]

(D) 1,3-Dienes undergo hetero Diels-Alder reactions with SO2 at low temperature in the presence of an acid promoter, such as CF3CO2H or BF3·Et2O, leading to sultines. [10]

(E) Allyl tin derivatives undergo ene reactions with sulfur dioxide, furnishing tin allyl sulfinates. [11] Recently, it was shown that allylsilanes and enoxysilanes derived from aldehydes, ketones and esters also produce ene adducts with SO2. [12] The silyl sulfinates from ene reactions can be brominated (Br2 or NBS) or chlorinated (Cl2 or NCS) to produce the corresponding sulfonyl halides. The latter ­react with primary or secondary amines or alcohols to give the ­corresponding sulfonamides or sulfonic esters (one-pot, three-component syntheses). [13]

(F) Sultines 2, arising from HDA reactions between dienes 1 and SO2, can be quenched with carbon nucleophiles such as enoxy­silanes or allylsilanes to give silylsulfinates 4. Desilylation of 4 and reaction with carbon electrophiles generates polyfunctional sulfones in one-pot, four-component operations. [14] Alternatively, 4 can be oxidized with NCS and reacted with amines or alcohols to produce polyfunctional sulfonamides 6 or sulfonic esters 7, ­containing up to three stereogenic centers. Hydrolysis of silyl ­sulfinates 4 and subsequent desulfitation generates polyketides and analogs 8, also in one-pot operations. [15]

   Permissions and Reprints All articles of this category