Bis(thiophosphinic amidate) complexes (i.e., 1) of representative group 3 and lanthanide metals have been quantiatively prepared in situ from the corresponding thiophosphinic amides and Ln[N(TMS)2]3. These unusual pentacoordinate complexes exhibit very high activity as catalysts for intramolecular alkene hydroamination.

The gold(I)-catalyzed cycloisomerization 1,5-enynes and 1,4-allylallenes to tetracyclododecane and tetracyclotridecane derivatives is reported. Complexation of the cationic gold(I) complex to either the alkyne or the allene moiety induces an intramolecular addition of the alkene leading to gold(I)-stabilized carbenoid intermediate. This intermediate undergoes a formal sp 3 -C-H insertion to generate the tertacyclic adduct. A series of deuterium labeling experiments show that the C-H functionalization step proceeds with an inverse kinetic isotope effect.Cationic gold(I) complexes have emerged as powerful π-acids capable of promoting a diverse range of enyne cycloisomerization reactions. 1 In these reactions, the gold catalyst not only serves to activate the alkyne towards nucleophilic addition,2 but also plays a role in stabilizing the cationic intermediates produced in the cyclization event.3 In many of these cases, the stabilization arises from interaction of the gold catalysts with the directly bonded carbocation. 4 Thus, transformations in which these intermediates display reactivity that is reminiscent of electrophilic metal-stabilized carbenes have been developed. 5,6 However, in contrast to other electrophilic metal-carbenoid species, insertion of the gold-stabilized cationic intermediates into sp 3 -C-H bonds is rare. 7,8 We envisioned that access to such a transformation might provide horino@eng.u-toyama.ac.jp, fdtoste@berkeley.edu. With the aim of examining the potential of cationic gold(I)-carbenoid intermediates to participate in this class of reactions, we revisited the gold-catalyzed cycloisomerization of 1,5-enynes A. 10 While we had previously observed that gold-catalyzed cycloisomerizations of cyclobutane and -pentane derived enynes (A, n=1,2) were terminated by a ring expansion to afford C ,10b we postulated that larger more flexible rings might allow for an intramolecular C-H insertion via gold-carbenoid intermediate B (eq 1). NIH Public Access(1)In order to explore this hypothesis, 1,5-enyne 1a possessing cycloheptyl skeleton at the C4 position was allowed to react under our standard conditions (2% (Ph 3 P)AuCl/AgSbF 6 ) for cycloisomerization of 1,5-enynes (eq 2). We were pleased to find that the reaction proceeded smoothly to provide tetracyclic compound 2a in 75% yield after one hour. On the basis the observation that electron donating ligands are preferred for reactions involving trapping of the gold(I)-carbenoid intermediates, we examined N,N-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) and tri(tert-butyl)phosphinegold(I)chloride as catalysts. Gratifyingly, both of these complexes showed improved reactivity (10-15 minutes) in the cycloisomerization reaction and produced 2a in better yield. Notably, in all cases, neither competing deprotonation from gold-carbenoid intermediate B to afford spiro[5.6]dodeca-1,4-diene nor 1,2-alkyl shift to provide ring expansion product (C) were observed.Under these optimized reactions conditions, a number of cycloheptyl or cyclooctyl-substitu...

Commercially available lanthanum tris[bis(trimethylsilyl)amide] has been shown to be a very effective catalyst for hydrosilylations of representative alkenes and dienes in the presence of PhSiH3.

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