On the control of secondary carbanion structure utilising ligand effects during directed metallation

• Andrew E. H. Wheatley,
• Jonathan Clayden,
• Ian H. Hillier,
• Alison Campbell Smith,
• Mark A. Vincent,
• Laurence J. Taylor and
• Joanna Haywood

Beilstein J. Org. Chem. 2012, 8, 50–60, doi:10.3762/bjoc.8.5

• deprotonating the substituent at the benzylic (or α-) position (“lateral lithiation”) through the directing group coordinating the incoming organometallic substrate whilst conjugatively withdrawing electrons from the benzylic group [2]. In the case of lateral reaction, stabilisation of the resulting anion is

• -position is not blocked (contrast this scenario with the conversion of 4-H into 4-Lil·3THF) recently led us to examine the hitherto unachievable formation of tertiary carbanions by directed lateral lithiation [16][17]. Accordingly, 2-isopropyl-N,N-diisopropylbenzamide (5-H) has been used to source 5-Lil·L

Carbamate-directed benzylic lithiation for the diastereo- and enantioselective synthesis of diaryl ether atropisomers

• Abigail Page and
• Jonathan Clayden

Beilstein J. Org. Chem. 2011, 7, 1327–1333, doi:10.3762/bjoc.7.156

• ; diastereoselective; enantioselective; lateral lithiation; metallation; Introduction One of the first uses of the chiral diamine (−)-sparteine (1) in its now familiar role of controlling asymmetric deprotonation/electrophilic quench reactions [1] was an enantioselective benzylic deprotonation of bis(2,6

Selectivity in C-alkylation of dianions of protected 6-methyluridine

• Ngoc Hoa Nguyen,
• Christophe Len,
• Anne-Sophie Castanet and
• Jacques Mortier

Beilstein J. Org. Chem. 2011, 7, 1228–1233, doi:10.3762/bjoc.7.143

• report herein that sequential ring lithiation/methylation of the simple protected uridine 1 leading to 2 followed by lateral lithiation/alkylation with ω-alkenyl bromides provides a useful regioselective chain-extension procedure and an efficient route to 3. Results and Discussion Most methods for the

• Li2CuCl4 [16][17][18] to 11 followed by quenching with 4-bromobut-1-ene failed to produce 3a. Consequently, lateral lithiations were examined. Lateral lithiation of benzenoid aromatics requires a stabilizing group capable of either delocalizing negative charge or stabilizing an organolithium by

• alkyl halides may result from steric hindrance [24][27]. Recently, the lateral lithiation of 4-hydroxy-6,7-dimethoxy-8-methyl-2-naphthoic acid was applied to the regioselective efficient construction of a series of 5,5'-didesisopropyl-5,5'-dialkylapogossypol derivatives that are potent pan-active