Fagnou and coworkers reported a Pd-catalyzed benzylation reaction of a variety of aromatic heterocycles, including thiazoles, thiophenes, indolizines, imidazopyrimidines, triazoles, oxazoles, and furans. Traditional methods for this transformation involve either Friedel-Crafts alkylation (requires strong Lewis or Bronsted acids and invariably precludes use of electron-deficient substrates) or deprotonation and addition of an electrophile (in both methods protection of acid- and base-sensitive functionalities is necessary, respectively). In this Pd-catalyzed process, benzylic chlorides are the most optimal electrophiles and in the presence of Pd(OPiv)₂, 2-diphenylphosphino-2'-(N,N-dimethylamino)biphenyl, Cs₂CO₃, and PivOH, a plethora of substrates are converted to the desired functionalized heterocycles in good to excellent yield. As expected, the method allows for increased functional group tolerance in the conversion of acid and base-sensitive substrates to their benzylated derivatives and selectivity was observed for reaction at the benzylic chloride over the aryl chloride in several instances.

Lapointe, D.; Fagnou, K. Org. Lett. ASAP.

Chatani and coworkers have reported a complementary method to the Sonogashira-coupling for the alkynylation of the ortho C-H bond of various anilides. In the presence of catalytic Pd(OAc)₂, AgOTf, and K₂CO₃, ortho-C-H-bond metalation takes place (stoichiometric evidence for this palladacycle), followed by addition of the Pd-intermediate to the bromo alkyne, generating a vinyl palladium species, which upon beta-bromo-elimination generates the alkynylated product. It should be noted that ligand exchange of the bromide for triflate is necessary to generate a species capable of electrophilic metalation on the substrate. A variety of substrates can be utilized in this transformation, providing unprecedented molecular complexity and flexibility for alkynylations of aromatic substrates. In addition, the –Si(i-Pr)₃ provides an additional functional group handle for further manipulation.

Tobisu, M.; Ano, Y.; Chatani, N. Org. Lett. 2009, ASAP.

Sames and coworkers have reported a Lewis-acid catalyzed [1,5] H-shift followed by C-C bond formation via reactive alkenyl oxocarbenium intermediates. Sames and coworkers have previously reported that expensive transition metal Lewis acids promoted cylizations of alpha,beta-unsaturated aldehydes and ketones, but were hampered with low yields and slow reaction times. The preparation of the corresponding acetals and ketals led to an improvement in the yield, reactivity and diastereoselectivity.  Thus, using the standard conditions of BF₃·Et₂O in CH₂Cl₂ at room temperature, a variety of tetrahydropyrans can be prepared, including those from more hindered and complex precursors. Finally, it was demonstrated that the acetals and ketals could be formed catalytically in situ when OHCH₂CH₂OH is added to the reaction mixture and that this method effects an increase in the rate (and in some cases, an increase in yield and diastereoselectivity) of the reaction, while also obviating the need for preparation of these precursors, and resulting in a binary catalytic system composed of BF₃·Et₂O as the catalyst and OHCH₂CH₂OH as the organocatalyst.

McQuaid, K. M.; Sames, D. J. Am. Chem. Soc. ASAP.

Ellman and coworkers have reported a Rh(I)-catalyzed arylation reaction of pyridines and quinolines. While the analogous alkylation they developed requires use of an electron-rich Rh-catalyst, the authors found it was necessary to switch to a catalyst system composed of an electron-deficient metal center           ([RhCl(CO)₂]₂) for optimal yields. The substrate scope was examined with respect to branching of the pyridine derivatives and aryl bromide coupling partners were examined in the quinoline couplings (including electron-rich and electron-poor aryl halides).  This C-H arylation method does not necessitate any prefunctionalization and provides the desired functionalized heterocycle in good yield.

Berman A. M.; Lewis, J. C.; Bergman, R. G. Ellman, J. A. J. Am. Chem. Soc. ASAP.