TMSCH₂Li and TMSCH₂Li−LiDMAE:  Efficient Reagents for Noncryogenic Halogen−Lithium Exchange in Bromopyridines

Abstract

TMSCH(2)Li and TMSCH(2)Li-LiDMAE have been used efficiently for bromine-lithium exchange in 2-bromo-, 3-bromo-, and 2,5-dibromopyridines under noncryogenic conditions, while low temperatures (-78 to -100 degrees C) are always needed with n-BuLi. The aminoalkoxide LiDMAE induced a remarkable C-2 selectivity with 2,5-dibromopyridines in toluene at 0 degrees C, which was unprecedented at such a temperature. The lithiopyridines were successfully reacted with electrophiles also under noncryogenic conditions giving the expected adducts in good yields.

Organolithium‐Initiated Polymerization of Olefins in Deep Eutectic Solvents under Aerobic Conditions

“…Althoughh igher-molecular-weight PS was obtained by using MeLi as initiator (entry 3, Table 2), both the broad distribution of molecular weight and the low yields observed clearly indicated the lower initiation performance of MeLi. If the reactionw as performed with Me 3 SiCH 2 Li, which shows ag entle reactivity comparedt ot he other basic organolithium reagents, [20] no polymerization product was observed (entry 4, Ta ble 2). Thus, on the basis of the experimentally obtained data (yield, M w ,a nd ), we can establish the activity of the initiator organolithium reagents in the polymerization of styrene with 1ChCl/2Gly as follows: nBuLi > secBuLi > tertBuLi > MeLi @ Me 3 SiCH 2 Li.…”

Combinations of Alkyllithiums and Lithium Aminoalkoxides for Generation of Functional Pyridine Organometallics and Derivatives

“…In this context, halogen-lithium exchange has received much attention, especially with 2,3-and 2,5-dibromopyridines, and efficient methodologies to control the exchange regioselectivity have been developed (Scheme 11). [47] Furthermore, LiDMAE acted as a stabilizing agent for the 2-lithiointermediates, thus avoiding isomerizations into the more stable species. [45,46] In addition to the potential isomerization of lithiated species, the formation of pyridyne through elimination of lithium bromide can also occur with 2,3-dibromopyridine if the reaction is performed under noncryogenic conditions (Scheme 12).…”

“…Besides halogen-lithium exchange with bromo-or iodopyridines, which has proven to be an efficient process, [1][2][3] deprotonative lithiation from the pyridine parent compounds also represents a straightforward route to functional derivatives. These multiple applications call for the availability of even more sophisticated compounds with easily tuneable properties for screening purposes.…”

“…In this context, regioselective lithiation has attracted much attention during the past decades because it offers fast access to numerous functional compounds. Besides halogen-lithium exchange with bromo-or iodopyridines, which has proven to be an efficient process, [1][2][3] deprotonative lithiation from the pyridine parent compounds also represents a straightforward route to functional derivatives. Unfortunately, the πdeficiency of pyridines has long limited the scope of this latter reaction, due to nucleophilic attack on the azomethine bond by alkyllithiums.…”

Spectroscopic and electrochemical behavior of newly synthesized high fluorescent symmetric 4′-nitrophenyl-3,4,9,10-perylenebisdiimide-azo hybrid dyes

“…Perylene pigments exhibit outstanding structural and functional properties including high electron mobility, high photo-and thermal stability, high fluorescence quantum yield, and high electron affinity [6,7]. These properties make perylene-based materials interesting candidates for a wide range of applications [8][9][10] such as porous materials [11], dye lasers [12], single molecule spectroscopy, [13] transistors (OFET), [14,15] light emitting devices, [16,17] photochromic, [18,19] sensors, [20] fluorescent markers, [21,22] solar energy collectors, [23] and liquid crystals. Perylenes are key chromophores for high-tech applications such as reprographic processes, [24] fluorescent solar collectors, [25] photovoltaic cells, [26] optical switches, [27] and lasers [28].…”