We find that a bulky pyridine-based catalyst promotes carbonate-forming reactions that ratchet the displacement of the macrocycle away from the reactive sites on the track. Under reaction conditions where both attachment and cleavage of the Fmoc groups occur through different processes, and the cleavage reaction occurs at a rate independent of macrocycle location, net directional rotation of the molecular motor continues for as long as unreacted fuel remains. We anticipate that autonomous chemically-fuelled molecular motors will find application as engines for molecular nanotechnology. 2, 19,20

We report the first room-temperature direct C-2 arylation of indoles with iodoarenes by using a highly electrophilic palladium catalyst generated in situ from Pd(OAc)2 and a silver carboxylate. These mild conditions permit a broad set of functionalities both in the indole and in the aryl iodide units such as free alcohols, phenols, aldehydes, bromides, or nitriles, thus allowing the synthesis of a variety of novel compounds in excellent yields.

We describe a three-compartment rotaxane information ratchet in which the macrocycle can be directionally transported in either direction along an achiral (disregarding isotopic labeling) track. Chiral DMAP-based catalysts promote a benzoylation reaction that ratchets the displacement of the macrocycle, transporting it predominantly to a particular end compartment determined by the handedness of the catalyst.

SIBX, the nonexplosive formulation of the lambda5-iodane 2-iodoxybenzioc acid (IBX), safely and efficiently mediates the hydroxylative dearomatization of various 2-alkylphenols and napthols into orthoquinols or their [4 + 2] cyclodimers. Reactions are typically run at room temperature using SIBX as a suspension in THF. Using these conditions, natural products such as the cyclodimer of the terpene carvacrol and, for the first time, the shikimate-derived (+/-)-grandifloracin were prepared in one step from their respective phenolic precursor.

No abstract

Direct arylations of pyridines are challenging transformations due to the high Lewis basicity of the sp 2 -nitrogen. Herein we report the use of carboxylates as weakly coordinating directing groups, facilitating the Pd-catalysed C-H arylation of this difficult class of substrates. This methodology allows regioselective C3/C4 arylation, without the need to use solvent quantities of the pyridine, and using low-cost chloro-and bromoarenes as coupling partners. Furthermore, carboxylates could be employed as traceless directing groups through a one-pot C-H arylation / Cu(I)-mediated decarboxylation sequence, thereby accessing directing group free pyridine biaryls.

A concise and efficient synthesis of the tetracyclic CDEF ring system of lactonamycin (1) is described. The key step involved the Lewis acid mediated, intramolecular Friedel-Crafts acylation of carboxylic acid 6 to produce the tetracyclic CDEF core structure of target 1. The synthesis of 6 was carried out using a high-yielding Negishi coupling of benzyl bromide 7 with triflate 8, which was accessible in 11 steps and 31% overall yield on a multigram scale starting from trihydroxy acid 9.

The [bis(trifluoroacetoxy)]iodobenzene-mediated oxidative dearomatization of 2-alkoxyarenols, followed in situ by trapping of the resulting arenoxenium ions by soft external carbon-based nucleophiles, constitutes a rapid access to highly functionalized naphthoid cyclohexa-2,4-dienones. These synthons can serve as valuable intermediates in the construction of the angularly-oxygenated benz [a]anthraquinone ABCD tetracyclic ring system of aquayamycin-like angucyclinones. This methodology so far has led to the elaboration of five-membered ring analogues of the ABC tricyclic unit of these natural products.