Palladium complexes of 1,3,5,7-tetramethyl-2,4,8-trioxa-6-phenyl-6-phosphaadamantane were prepared and characterized with Pd[1,3,5,7-tetramethyl-2,4,8-trioxa-6-phenyl-6-phosphaadamantane](2).dba shown to be an effective catalyst for use in the Suzuki and Sonogashira reactions and the alpha-arylation of ketones. Couplings using this versatile complex proceeded in excellent yields under mild conditions.

[reaction: see text] A new class of sterically hindered phosphines based on a phospha-adamantane framework is described. Arylation or alkylation of the 1,3,5,7-tetramethyl-2,4,8-trioxa-6-phospha-adamantane system allows for the preparation of tertiary phosphines suitable for use in palladium-catalyzed cross-coupling reactions. For example, use of a catalytic system incorporating Pd(2)(dba)(3) and 1,3,5,7-tetramethyl-2,4,8-trioxa-6-phenyl-6-phospha-adamantane is shown to promote the Suzuki cross-coupling of aryl iodides, bromides, and activated chlorides with a variety of aryl boronic acids at room temperature in a few hours with high yields.

This paper is dedicated to Professor Paul de Mayo on the occasion of his 60th birthday JAMES FREDERICK KING, JOHN HENRY HILLHOUSE, and STANISLAW SKONIECZNY. Can. J. Chem. 62, 1977Chem. 62, (1984. We present evidence that the reactions of ethenesulfonyl chloride ( I ) and trcrt~s-l -propene-l -sulfonyl chloride (3) with water in the presence of pyridine, trimethylamine, and a number of other tertiary amines proceed primarily by way of an initial + vinylogous substitution reaction to form the cationic sulFne, R.;NCHRCH=SOZ. which subsequently reacts with water either by addition (and deprotonation) to form the betaine R.;NCHRCHZSOI, or by vinylogous substitution (and deprotonation) to give the alkenesulfonate anion. CHR=CHSO, (R = H or CH3). Formation of,the latter represents the first well-supported example of vinylogous nucleophilic catalysis. These conclusions are drawn from kinetic and product composition observations, including ( ( I ) a-monodeuteration in the betaine and lack of deuteration of the ethenesulfonate (CHZ=CHSO,) from the reaction in DZO, fb) rate lowerings of up to 2000-fold for 2-(and 6-) substituted pyridines from those expected from Bronsted-type relationships shown by "unhindered" pyridine bases, (c) lack of a kinetic solvent isotope effect in the reaction of 1 with 3-cyanopyridine, (d) a lower rate of reaction of 3 vs. 1 not directly correlated with product composition, and (e) formation of similar product mixtures from either 1 or Pyr'CHZCHZSOZCI CI- (180) with aqueous pyridine. For the initial + formation of the sulfene, R3NCHZCH=SOZ, the available evidence does not distinguish between a two-step mechanism via an intermediate zwitterion and a closely related concerted reaction, but for the further reaction of the sulfene a process involving a zwitterionic intermediate common to both products is favoured. For the reaction of 1 or 3 in the absence of tertiary amines evidence is presented for a direct displacement on sulfur mechanism leading to the alkenesulfonate anion, plus a small proportion (up to 15%) of formation of the 2-hydroxy-I-alkanesulfonate anion by way of the sulfene HOCHRCH=SOZ (R = H or CH3).JAMES FREDERICK KING, JOHN HENRY HILLHOUSE et STANISLAW SKONIECZNY. Can. J . Chem. 62, 1977Chem. 62, (1984. On rapporte des donnCes qui suggkrent que la rCaction du chlorure d'6thknesulfonyle ( I ) et du chlorure de propkne-l sulfonyle-l trans (3) avec de I'eau, en prCsence de pyridine, de trimkthylamine et d'un certain nombre d'autres amines tertiaires, se produit principalement par le biais d'une rkaction initiale de substitution vinylogue conduisant i la formation du sulfkne cationique R;NCHRCH=SOZ, qui rkagit ensuite avec de I'eau soit par une addition (et une dCprotonation) pour former la bCtaYne R;NCHRCHZSO, soit par une substitution vinylogue (et une dCprotonation) pour donner I'anion alcknesulfonate, CHR=CHSO, (R = H ou CH3). La formation de ce dernier compose represente le premier exemple bien document6 d'une catalyse nuclCophile vinylogue. On tire ces conclusions en se basan...

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