The First Solid-State Structure of a Lithiated Diazomethane with C–Li and N–Li Bonds: {[Me3SiC(Li)N2]2·3 THF}∞

Abstract

Reaction of n‐butyllithium with Me3SiCHN2 in THF affords the first example of a lithiated diazomethane with C–Li and N–Li bonds.

Systematic Evaluation of 1,2-Migratory Aptitude in Alkylidene Carbenes

“…Initial DLPNO-CCSD­(T) computations established a thermally feasible pathway from acetophenone ( 1 -Me,Ph) to 1-phenylpropyne ( 6 -Me,Ph), Figure . Consistent with Colvin and Hamill’s original proposal and later work by Gilbert, the diazoalkene MePhCCN 2 ( 4 -Me,Ph) was identified as a key intermediate, formed via a nucleophilic addition, , [1,3]-silyl migration, and elimination sequence. Although the ionic nature of the intermediates mean that quantitative comparisons made in the absence of explicit solvation should be interpreted with caution, lithiated silyl ether 3 -Me,Ph appears to be marginally favored over lithium alkoxide 2 -Me,Ph (Δ G 195K = −5 kJ mol –1 ), in a delicately balanced [1,3]-Brook equilibrium, − , in which pre-equilibrium between lithium α-diazoalkoxide 2 -Me,Ph and cyclic siliconate 7 -Me,Ph is kinetically insignificant.…”

Enantiospecific Synthesis of the (9S,18R)-Diastereomer of the Leukocyte Adhesion Inhibitor Cyclamenol A

“…Finally, shorter than the Li−N(TMEDA) bonds previously noted for the bis ‐coordinating Lewis base molecules are those in which the TMEDA acts only as a monodentate donor [mean Li−N = 2.079 Å]. A comparison of the solid‐state structural parameters observed for 9 with those noted in 7 reveals that both C−N (mean 1.206 and 1.202 Å respectively for 9 and 7 ) and N−N (mean 1.214 and 1.208 Å) bond lengths correlate well but differ significantly from those in C ‐lithiated 1‐Li· 3 / 2 THF 19.…”

“…The reaction of 1‐H with n BuLi in THF yielded large yellow crystals of pure lithiated (trimethylsilyl)diazomethane 1 / 2 [{Me 3 SiC(Li)N 2 } 2 ·3THF] ( 1‐Li· 3 / 2 THF ), the solid‐state structure of which we have previously reported 19. X‐ray crystallography has shown 1‐Li· 3 / 2 THF to be a polymer based on a repeating tetramer unit (Figure 4), consisting of two ( mono ‐THF) complexed lithiodiazomethane molecules and two ( bis ‐THF) complexed ones i.e.…”

An Azide-Free Synthesis of Metallodiazomethanes Using Nitrous Oxide

“…Crystals of 2a – 2c could be obtained from saturated toluene solutions at low temperatures with 18-crown-6 (18-c-6, 2a ) or [2.2.2]cryptand ( 2b and 2c ) for additional coordination of the potassium cation (Figure and Table ). To the best of our knowledge, these are, aside from the silyl system II (Figure ), the only crystallographically characterized alkali metal diazomethanides reported to date. , While the cryptand complexes of 2b and 2c form ligand-separated ion pairs, the [K(18-c-6)] cation in 2a features a contact with the methanide carbon atom and an additional weak interaction with a phenyl-CH bond of an adjacent molecule in the crystal structure, resulting in the formation of a coordination polymer. The C–N bond lengths in the “naked” anions in 2b and 2c amount to 1.253(3) and 1.272(5) Å, which are shorter than those reported for TsC(H)N 2 (1.281 Å) or 3-methoxy-5-diazomethyl-pyran-4-one (1.299(2) Å) .…”