Organotin compounds offer many advantages for cross-coupling reaction, and it is thus not surprising that the palladium-catalyzed procedure introduced and developed by the late John Stille was seized upon by preparative organic chemists and used to great advantage for synthetic elaborations. Stille himself reviewed the area in 1986 [ 111, but his untimely death in July 1989 cut short his own work on the reaction which now bears his name. The present author attempted to cover the progress of the "Stille reaction" over the period 1986-mid-1991 in a review published in 1992 [2], and the publication of this monograph provides an opportunity to take another critical look at the applications of the procedure.In the early days various palladium catalyts were used, Pd(PPh,), and PhCH,PdCI(PPh,), being the two which were most frequently applied. A considerable amount of work has since gone into catalyst refinement, and here the name of V. Farina must be mentioned; he has published a number of important papers, and also reviewed his work and that of others [3]. Readers who wish to keep themselves up to date in this area in the future must hope that L. S. Hegedus will "keep up the good work' and continue to publish his invaluable annual surveys on the use of transition metals in organic synthesis [4] which always contain a section on tin compounds.Though strictly speaking outside the scope of this chapter, some brief details of other palladium-catalyzed reactions of organotin compounds (ditins and tin hydrides) will be given, as these can provide potentially useful reagents for Stille reactions. Many transition metals have found their niche in organic synthesis, but as far as reactions of organotins are concerned only palladium has been used to a large extent. However, relevant reactions of two other transition metals, copper and nickel, will be referred to at the end of this survey.One of the beauties of the Stille procedure is that various organic residues (alkyl, aryl, vinyl, alkynyl, etc.) can be transferred from tin to carbon in cross-couplings; although papers still continue to appear which deal with the transfer of more than one type of residue, "dedicated" papers whose goal is a particular type of elaboration are more common, and indeed there is a type of "hit list" reflecting the popularity of certain groups. Alkenyltins are by far the most important on this list, and we shall start by discussing their use; subsequent sections will mirror the range of application of other types of organotin.
Stille Coupling of AlkenyltinsAlkenyltins can undergo coupling with a wide variety of organic halides and triflates and with acid chlorides. Although most of the examples reported deal with intermolecular coupling, intramolecular coupling is finding increasing favor, particularly as a step in 167 Metal-catalyzed Cross-coupling Reactions Edited by François Diederich, Peter J. Stang
4 Orgunotin Reqents in Cross-couplingnatural-product synthesis. The presence of two stannyl groups on the ethene unit offers synthetic advantages...