Lithium dialkylamides. 13C parameters and slow proton transfer

Synthesis of Phenacene–Helicene Hybrids by Directed Remote Metalation

“…60 In DoM reactions, s-BuLi (pK a = 51) and LiTMP (pK a = 37.3) 65 are the most commonly used bases. 66 In the present work, they were chosen over LDA (pK a = 35.7) 67 based on their base strength, for the previous studies reported pK a > 37.2 for ortho C−H bonds in monosubstituted benzenes with strong DMGs. 65 With the iodo-coupling partners 2a and 2b in hand, focus was on the preparation of the three regioisomers of methylnaphthalenyl boronates.…”

Effects of Base, Electrophile, and Substrate on the Selective Alkylation of Heteroaromatic Systems

“…Amine size also plays a role in the kinetics of the process, with rates of proton transfer being faster for smaller amines. 11 Several of the bases surveyed (LiNEtMe, LiNEt 2 , LiN n Pr 2 , and LiNEt i Pr) fall within the useful window for this particular transformation and give excellent levels of selectivity for the thermodynamic product 10 Prompted by an apparent discrepancy in the literature (Scheme 2), we also investigated the effect of electrophile choice on the regioselectivity of these alkylations. In 1983 Hamana and Sugasawa reported 12 that treatment of 2-methyl-4-phenyloxazole (5) with n-BuLi at -78 °C followed by addition of benzaldehyde gave alkylation only at the C 5 -ring position (13a).…”

Combinations of Alkyllithiums and Lithium Aminoalkoxides for Generation of Functional Pyridine Organometallics and 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. To overcome this side-reaction and to promote lithiation, alternatives such as the use of sterically hindered LDA [4][5][6][7][8][9] or LTMP [10][11][12][13][14] have been proposed. Unfortunately, equilibrated reactions were observed, implying trapping of lithiopyridines in situ.…”