Activation of Low-Valent Titanium Reagents with Iodine:  Facile Low-Temperature McMurry Reaction and N/O-Debenzylation/Deallylation

Abstract

A highly reactive, low-valent titanium (LVT) reagent has been prepared by the addition of substoichiometric amounts of iodine to the LVT species generated by Rieke's method (TiCl3−Li−THF). While the conventional McMurry reaction requires high temperatures and prolonged reaction times for the generation of olefins, the present activated LVT reagent is able to effect the reductive coupling of aliphatic as well as aromatic carbonyls to the corresponding olefins at lower temperatures and much reduced reaction times. The protocol is also useful for the intramolecular coupling reactions leading to the one-step synthesis of heterocycles. The temperature-controlled McMurry reaction provides enhanced diastereoselectivity and features an excellent chemoselectivity. In addition to the McMurry reaction, other SET-induced carbon−heteroatom (O, N) bond cleavages can also be carried out with the activated reagent at a fast rate and at a low temperature in high yields.

Exclusive Synthesis of β‐Alkylpyrroles under Indium Catalysis: Carbonyl Compounds as Sources of Alkyl Groups

“…[14] For example, the treatment of 4 m, 4 t, or 7 f with TiCl 3 /Li/I 2 in THF at room temperature gave 8 a, 8 b, or 8 c, respectively, [15] indicating that the debenzylation and decumylation allow us to gain nitrogen-unsubstituted b-alkylpyrroles with all types of alkyl groups, that is, primary, secondary and tertiary ones.…”

Broadening the chemical scope of laccases: selective deprotection of N-benzyl groups

“…N-benzyl groups are typically cleaved using reductive methods, with palladium-catalyzed hydrogenolysis often employed. 1,[3][4][5][6][7] Also oxidative or photolytic debenzylations can be carried out with a variety of reagents such as cerium ammonium nitrate (CAN), 8 diisopropyl azodicarboxylate (DIAD), 9 titanium(III) chloride in combination with iodine, 10 or alkali metal bromide formed mixing KBr and Oxone ® , 11 among others. Finally, Lewis acids such as boron reagents have also been applied to this process.…”

Reductive coupling of carbonyl compounds promoted by cobalt or titanium nanoparticles

“…Isolated yields for compounds 4 are given in Table 2. The following known compounds included in Table 2 were characterised by comparison of their chromatographic and spectroscopic data ( 1 H, 13 C NMR, and MS) with those described in the literature: 1,2-diphenyl-1-ethene 4a, 19 1,2-di(4-chlorophenyl)-1-ethene 4b, 21 1,2-bis-[4-(dimethylamino)phenyl]ethene 4k, 22 1,2-di(2-furyl)-1-ethene 4l, 23 2,3-diphenyl-2-butene 4g, 24 2,3-di(2-naphthyl)-2-butene 4m, 21 3,4-dimethyl-1,6-diphenyl-1,3,5-hexatriene 4i, 25 1,2-diphenyl-1-cyclohexene 4h, 26 1,2-divinyl-1-cyclohexene 4n, 27 5,6-dibutyl-5-decene 4o.…”