High chemoselectivity in the phenol synthesis

• Matthias Rudolph,
• Melissa Q. McCreery,
• Wolfgang Frey and
• A. Stephen K. Hashmi

Beilstein J. Org. Chem. 2011, 7, 794–801, doi:10.3762/bjoc.7.90

• 10.3762/bjoc.7.90 Abstract Efforts to trap early intermediates of the gold-catalyzed phenol synthesis failed. Neither inter- nor intramolecularly offered vinyl groups, ketones or alcohols were able to intercept the gold carbenoid species. This indicates that the competing steps of the gold-catalyzed

• ][24][25]. Moreover, interesting new pathways were opened when ynamides and alkynyl ether substrates were employed: Here A is also a possible intermediate along these pathways [25]. Since direct experimental evidence existed only for C and D, we intended to intercept the postulated carbenoid

• Intermolecular olefinic trapping reagents We started with the simplest experiments, namely the intermolecular trapping of the gold carbenoid intermediates. When 3 was reacted in the presence of an activated olefin, such as norbornene or styrene, phenol 4 was formed exclusively in essentially quantitative yield

Solvent- and ligand-induced switch of selectivity in gold(I)-catalyzed tandem reactions of 3-propargylindoles

• Estela Álvarez,
• Delia Miguel,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez,
• Félix Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2011, 7, 786–793, doi:10.3762/bjoc.7.89

• esters have been extensively investigated. In these processes the gold-carbenoid species generated are able to undergo a wide variety of further transformations [8][9][10][11]. In addition, propargylic sulfides have also been reported as useful substrates for this type of process, participating in

• reactions of propargylic systems. Thus, 3-propargylindoles 1 give rise to α,β-unsaturated gold-carbenoid intermediates 2 that evolve through different pathways depending on the substituents at the propargylic and terminal positions of the alkyne moiety (Scheme 1). If (hetero)aromatic substituents are

• setting of the reaction conditions (modulation of the electronic properties of the ligands, counter ion, solvent, substitution pattern of the substrates, etc.). Herein, we report our efforts to control the two competing pathways in the evolution of gold-carbenoid intermediates generated by an initial 1,2

Synthetic applications of gold-catalyzed ring expansions

• David Garayalde and
• Cristina Nevado

Beilstein J. Org. Chem. 2011, 7, 767–780, doi:10.3762/bjoc.7.87

• , intermediates characterize these competitive processes, i.e., 1,2-migration via metal "carbenoid" 81 formation and [3,3]-sigmatropic rearrangement via allenyl acetate 82 as an intermediate (Scheme 24) [5][56][57]. In 2008, Toste and co-workers reported a gold(I)-catalyzed cycloisomerization of cis-pivaloyloxy

When cyclopropenes meet gold catalysts

• Frédéric Miege,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2011, 7, 717–734, doi:10.3762/bjoc.7.82

• undergo subsequent ring-opening to produce an organogold species that can be viewed as a hybrid between a gold-stabilized allylic carbocation B and a gold carbene C. The organogold carbenoid species generated by the ring-opening of cyclopropenes can participate in a variety of reaction types such as

• ) carbenoid complexes, Toste et al. highlighted the importance of the substitution pattern and the ligands (Scheme 4). Interestingly, DFT calculations were carried out for organogold species that can actually be generated by ring-opening of cyclopropenes, and therefore the authors examined experimentally the

• reflux [33][38]. These reactions appear to constitute the first examples of intramolecular olefin cyclopropanation promoted by a silver carbenoid generated by ring-opening of a cyclopropene. We envisioned that the gold carbene resulting from the ring-opening of appropriately substituted cyclopropenes

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• insertion The laboratory of G.A. Sulikowski proposed a synthesis of 1,2-aziridinomitosenes [106][107] using as key transformations a Buchwald–Hartwig cross-coupling [108][109][110] and a chemoselective intramolecular carbon-hydrogen metal-carbenoid insertion reaction (Scheme 39). The chiral pyrolidine 136

Synthesis of highly substituted allenylsilanes by alkylidenation of silylketenes

• Stephen P. Marsden and
• Pascal C. Ducept

Beilstein J. Org. Chem. 2005, 1, No. 5, doi:10.1186/1860-5397-1-5

• carbenoid-based reagents. Introduction Allenylsilanes are versatile intermediates for organic synthesis.[1][2] They have two main modes of reactivity: firstly, as propargyl anion equivalents in thermal [3][4] or Lewis acid-mediated [5][6] addition to carbonyls, acetals and imines, and secondly as three

• problem, it gave us the encouragement to screen other titanium carbenoid-based methylenating reagents. The Petasis reagent (dimethyltitanocene) [31][32] was our next choice, and we were pleased to find that it afforded modest to excellent yields of the allenylsilanes in reaction with most of the ketene