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N-Heterocycles
Published in Navjeet Kaur, Metals and Non-Metals, 2020
Tsuchida et al. [76] investigated double cyclization of allylaminoalkenes through tandem aminolithiation-carbolithiation using lithium amide as a protonating agent as well as a lithiating agent to synthesize hexahydro-1H-pyrrolizine and bicyclic octahydro-indolizines in good diastereoselectivity and high yields (Scheme 31). The reaction was stopped using lithium amide in catalytic amounts, after the aminolithiation step, to afford the monocyclic product, whereas the bicyclic to monocyclic ratio increased when lithium amide was utilized in increased amounts. The yield of bicyclic product improved with increased diastereoselectivity when a bulkier amine (tert-butyltritylamine) was used.
Basic Chemistry for the Synthesis of Telechelic Polyesters and Polycarbonates
Published in Sophie M. Guillaume, Handbook of Telechelic Polyesters, Polycarbonates, and Polyethers, 2017
Recently, the anionic polymerization of ethylketene has been reported as an efficient method for synthesizing polyester [36]. Therein, sodium naphthalenide, alkyl lithium, lithium alkoxide, and lithium amide are examined as initiators. Although its living nature has been not clarified yet, it is interesting as a potential method for synthesizing telechelic polyesters with a unique main chain.
Introduction
Published in Shitanshu Sapre, Kapil Pareek, Rupesh Rohan, Compressed Hydrogen in Fuel Cell Vehicles, 2022
Shitanshu Sapre, Kapil Pareek, Rupesh Rohan
Nitrides, amides and imides (Li–N–H)-based systems with three stoichiometric ternary compounds: lithium imide (Li2NH), lithium amide (LiNH2) and lithium nitride hydride (Li4NH) for hydrogen storage were reported by Chen et al. [26]. Li3N+2H2→Li2NH+LiH+H2↔LiNH2+2LiH Dehydrogenation of the imide requires high vacuum and temperatures above 600 K [26]. These are unsuitable conditions for reversible hydrogen storage, but the reaction between the imide and the amide is reversible under more moderate conditions of both temperature and pressure. A number of other similar materials have been studied as hydrogen storage media, including the ternary compounds Mg(NH2)2, RbNH2, CsNH2 and Ca–N–H, and the quarternary and higher systems Li–Ca–N–H, Li–Al–N–H, Na–Mg–N–H, Na–Ca–N–H, Mg–Ca–N–H and Li–Mg–Ca–N–H [23]. It can be seen that these materials have the potential to provide high gravimetric storage capacities and are therefore of great interest. However, the Li–N–H system suffers from some drawbacks, including high hydrogenation and dehydrogenation temperatures, and air or moisture sensitivity. Another is the evolution of ammonia during the dehydrogenation reaction [27].
Reactions between lithiated 1,3-dithiane oxides and trialkylboranes
Published in Journal of Sulfur Chemistry, 2021
Basil A. Saleh, Keith Smith, Mark C. Elliott, Gamal A. El-Hiti
Next, our attention turned to the use of less nucleophilic lithium reagents such as lithium diisopropylamide (LDA), lithium tetramethylpiperidide (LiTMP) and lithium bis(trimethylsilyl)amide (LiHDMS). First, we attempted reaction of 5 and LDA followed by protonation. Only starting material was recovered, indicating that 5 did not undergo thiophilic addition such as was seen with sec- and n-BuLi. However, when the lithiated intermediates were treated with trioctylborane the yields of 10 were still disappointingly low (Table 1; Entries 8–12). The best yield of 10 with the lithium amide reagents was 30% when the reaction was carried out with LDA (1.1 equivalents) at 0°C (Table 1; Entry 9). The use of a superbase (Schlosser’s reagent, LICKOR [36]) provided no improvement.