Studies in our organometallic subgroup are aimed at the design and development of new catalytic reactions, with an emphasis on processes that, in the absence of catalysts, would be forbidden or would require harsh conditions. [1,2] These studies have thus far produced the first examples of transition-metal-catalyzed [4þ4] cycloadditions of bisdienes, [3] [4þ2] cycloadditions of dienynes (and diene allenes), [4] [5þ2] cycloadditions of vinylcyclopropanes and p systems, [5] and [6þ2] cycloadditions of vinylcyclobutanones and p systems.[6] Recently, we started to investigate whether these and other two-component [mþn] cycloadditions could be converted into multicomponent [mþnþo…þx)] processes through trapping of the organometallic intermediates with additional components. [7] These investigations have thus far led to the first metal-catalyzed, three-component [5þ2þ1] cycloaddition reactions based on trapping of an intermediate in the [5þ2] cycloaddition reaction with CO.[8] The current study was directed at determining whether intermediates in the [4þ2] cycloaddition of dienynes could be similarly trapped with CO.Outlined in Scheme 1 are three competing metal-catalyzed cycloaddition pathways available for a dienyne in the

The triple reuptake inhibitor GSK1360707F was synthesized via an efficient and scalable route that features an enyne cycloisomerization reaction catalyzed by either Pt(II) or Au(I). Key aspects of this work such as the choice of the nitrogen protecting group and initial enantioselectivity studies are discussed.

The transition-metal-catalyzed activation of carbon-carbon (CÀC) sigma bonds represents an important and fundamental challenge in organometallic chemistry that has the potential to broaden how we approach problems in organic synthesis. [1] We have previously shown that transition metals can be used to catalyze the strain-assisted CÀC bond activation of vinylcyclopropanes (VCPs) to produce organometallic intermediates that can be intercepted with various trapping agents to afford new two-, three-, and four-component cycloadditions. Representative examples include the [5+2] cycloaddition of VCPs and p systems (Scheme 1a);[2] the [5+2+1] cycloaddition of VCPs, alkynes (and allenes), and CO; [2c, 3] and the [5+1+2+1] cycloaddition of VCPs, alkynes, and CO, [4] thus providing new routes to seven-, eight-, and nine-membered rings and their derivatives.[5] Whereas the extension of this five-carbon VCP chemistry to simple six-carbon vinylcyclobutanes has failed thus far (Scheme 1 c), the metal-catalyzed activation of the CÀC bond of vinylcyclobutanones has been successful, thus leading to a new [6+2] cycloaddition for the formation of eight-membered rings (Scheme 1 b). [6,7] To explore whether vinylcyclobutanes could be activated for use as six-carbon components in metal-catalyzed reactions, we examined the reaction of 1-siloxy-1-vinylcyclobu-

Silver(I) bis[(benzyloxy)imidazol-2-ylidene] complex 6 is prepared by reaction of an alkoxyimidazolium bromide (4) with Ag2O. In situ deprotonation of the alkoxyimidazolium bromide 4 afforded the rhodium(I) and palladium(II) complexes 7 and 8, whose structures were verified by X-ray crystallography. Rhodium(I) (benzyloxy)imidazolylidene complex 7 efficiently catalyzes the [5+2] cycloaddition reaction of an yne−vinylcyclopropane (93%) and the [4+2] cycloaddition reaction of a diene−yne (99%) at room temperature in minutes.