Cyclopropylmethyl- and cyclobutylmethyllithium by an arene-catalyzed lithiation. Stability and reactivity

Reactivity and mechanism in the ring-opening of cyclopropylmethylplatinum(IV) complexes

“…Transition metal complexes containing cyclopropylmethyl or cyclobutylmethyl ligands are often invoked as reaction intermediates in these reactions, and the products may contain either the intact cycloalkyl ring or a ringopened form [1,2]. The transition metal may play a direct role in the ring-opening step, but it is also well known that cyclopropylmethyl to butenyl isomerisation may occur within the organic free radicals, cations or anions [3][4][5][6]. Some insights into the mechanisms have been gained by study of stoichiometric reactions, but there are still surprisingly few known examples of thermally stable transition metal complexes with cyclopropylmethyl or cyclobutylmethyl ligands to act as model compounds [7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

“…Thus, the reaction of [PtMe 2 (bipy)], 1, with a 20-fold excess of a 1:1 mixture of cyclopropylmethyl and cyclobutylmethyl bromides gave complex 2, with none of complex 3 detectable by 1 H NMR. The large neighboring group effect of the cyclopropyl substituent [25][26][27] and the absence of ring opening during the oxidative addition [3][4][5][6] both support an S N 2 mechanism of oxidative addition [28,29]. The 2-butenyl bromide was an 85:15 mixture of E and Z isomers and the ratio of products 5:6 was 80:20, indicating that the alkene stereochemistry is retained during the oxidative addition and that the Z-2-butenyl bromide reacts slightly faster.…”

“…These complexes were all thermally stable in solution at room temperature, and the cyclobutyl derivative 8 was also stable in refluxing methanol but the cyclopropyl derivative 7 did undergo ringopening to give 9 (as a mixture of isomers 9a and 9b, Scheme 2) under these conditions. Reaction of complex 2 with silver hexafluorophosphate in methanol is expected to give initially the cationic complex [PtMe 2 (CH 2 -c-C 3 H 5 )(MeOH)(bipy)][PF 6 ], but the product isolated at room temperature was identified by NMR as mostly the ring-opened isomer [PtMe 2 (CH 2 CH 2 CH=CH 2 )(MeOH)(bipy)][PF 6 ]. This could not be isolated in pure form but it was positively identified by reaction with lithium bromide to give the stable complex 4.…”

(E)‐Dimethyl 2‐Oxopent‐3‐enylphosphonate: An Excellent Substrate for Cross‐Metathesis – Easy Access to Functionalized Heterocycles

“…CH 2 Cl 2 was distilled from CaH 2 , and Et 2 O and THF were distilled from sodium/benzophenone. Phosphonate 1 [15] and olefins 2c, [20] 4b, [21] 4c, [22] 4e, [21] 4f, [23] 7a, [22] 7c, [22] 7d, [24] 7e, [25] 7f, [26] 7g, [26] 7h, [27] and 7i [28] were obtained following existing procedures. Other reagents were obtained from commercial suppliers and used as received.…”

Conversion Reaction of Benzyl-Type Chlorinated Hydrocarbons into Functional Groups

“…The reaction of alkyl halide with lithium in non-polar solvent with good selectivity has ben reported in many papers. Yue and his group members have done a lot of researches since 1996 [9][10][11][12][13][14] .…”