Download (direct link):
NMR nuclear magnetic resonance
ppb parts per billion
PTC Phase transfer catalysis
rt room temperature
Tf Inflate (trifluoromethanesulfonate)
TLC thin-layer chromatography
TMEDA N, N,N',N '-tetrame thylethylenediamine
TMSOTf trimethylsilyl triflate
TOMAC trioctylmethylammonium chloride
TsOH p-toluenesulfonic acid
UDP ultrasonically dispersed potassium
Organic chcmists spend an important part of their time doing synthetic work. Considerations on the philosophy and practice of organic synthesis, its logic and prospects are discussed in every advanced textbook on organic chcmistry and are often presented at more sophisticated levels in general papers by scientists themselves (see  and  for elaborate reflections on the subject). Because of this, the search for new synthetic methods and reagents and their uses in synthetic methodology is an active area in chemistry. Over the last two or three decades the importance of heterochemistries in synthesis has increased dramatically. Phosphorus and silicon chemistries were developed earlier and faster than selenium and sulfur chemistries. The reluctance of organic chemists to handle selenium and sulfur compounds was probably in part responsible for such a situation; however, this time is now over. A devoted chemist can no longer ignore the possibilities offered by sulfur-based reagents, and, indeed, sulfur ylides and sulfur-stabilized carbanions arc widely known and used, but what of other reagents? Derivatives of thiocarbonyl compounds, for instance, have not received the consideration that, we believe, they deserve, although the Barton deoxygenation reaction has contributed to popularize these types of compounds.
The aim of this book, which we purposely wanted to keep small in size, is to present some aspects of the chemistry of sulfur reagents. We have selected a few excerpts, and we are aware that our choices are arbitrary— to give hints on the tremendous, and still largely unexplored, potentiality of sulfur-mediated synthesis, particularly for complex molecules, with examples of the very recent literature (more than one-third of the experimental procedures given in the text were published in 1991-1993). were our main guides. Yields, selectivities (chemo-, regio- and stereoselectivity), scale and scope of the reactions were taken into consideration, and in some eases our personal views on their interest. We hope that the reader will share our enthusiasm for sulfur chemistry and think of using it in his or her daily work. The rewards could be great, for.
as the poet said, do not forget:
Col Zolfo Giove combattfe i Titani.
11 Zolfo (Vincenzo Masini, 1759)
We would like to thank the following editors and publishers for their kind permission to reproduce material from their periodicals, as quoted in the text with reference to the authors and journals.
American Chemical Society, 1155 16th Street, N. W., Washington, DC 20036, USA.
Belgian Chemical Societies.
Elsevier Science Ltd, The Boulevard, Langford Lane, Kidlington 0X5 1GB, UK.
Elsevier, 29, rue Buffon, 75005 Paris, France.
Georg Thieme Verlag, Riidigerstrasse 14, D-70451 Stuttgart, Postfach 301120, Germany.
Marcel Dekker Inc., 270 Madison Ave., New York 10016, USA.
Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF, UK.
The Chemical Society of Japan, 1-5, Kanda-Surugadai, Chiyoda-ku, Tokyo 101, Japan.
The Royal Netherlands Chemical Society.
VCH, Postfach 101161, D-69452 Weinheim, Germany.
Preparation of Organosulfur Reagents
The reaction of elemental sulfur with organometallic compounds is one of the standard methods of synthesis of thiols [3, 4]. In this way, the ortho lithiation of lithium benzenethiolate led to the preparation of 1,2-benzenedithiol (1), and a convenient one-pot procedure which can be used on a large scale was worked out .
Under an inert atmosphere, benzenethiol (0.103 1, lmol) was added dropwise to a vigorously mechanically stirred solution of TMEDA (0.1661,
1.1 mol) and n-BuLi (1.37 1 of a 1.6 ě solution in hexane, 2.2 mol) in hexane (0.501) at 0°C. After 1 h, the ice bath was removed and the stirring continued at room temperature for 20 h. The resulting cloudy off-white mixture was cooled to -20°C (ice/EtOH bath), after which sulfur (32g, 1 mol) was added portionwise through a Gooch tube. The resulting yellow suspension was stirred at -20°C for 2h and 20h at room temperature. The viscous yellow reaction mixture was recooled to -20°C and carefully quenched with a mixture of ice (0.50 1) and HC1 (0.40 1, 3 N, 1.2 mol). The aqueous layer was separated and extracted with ether (3 X 30 ml) and the combined pale-yellow organic layers were dried (MgS04). Volatile