2,4-lutidine hydrochloride

Dried with Linde type 5A molecular sieves, BaO or sodium, and fractionally distd. The distillate (200g) was heated with benzene (500mL) and cone HCl (150mL) in a Dean and Stark apparatus on a water bath until water no longer separated, and the temperature just below the liquid reached 80°. When cold, the supernatant benzene was decanted and the 2,4-lutidine hydrochloride, after washing with a little benzene, was dissolved in water (350mL). After removing any benzene by steam distn, an aqueous soln of NaOH (80g) was added, and the free... 

Catalytic turn-over [59,60] in McMurry couplings [61], Nozaki-Hiyama reactions [62,63], and pinacol couplings [64,65] has been reported by Fiirst-ner and by Hirao by in situ silylation of titanium, chromium and vanadium oxo species with McaSiCl. In the epoxide-opening reactions, protonation can be employed for mediating catalytic turn-over instead of silylation because the intermediate radicals are stable toward protic conditions. The amount of Cp2TiCl needed for achieving isolated yields similar to the stoichiometric process can be reduced to 1-10 mol% by using 2,4,6-collidine hydrochloride or 2,6-lutidine hydrochloride as the acid and Zn or Mn dust as the reduc-tant (Scheme 9) [66,67]. 

A protocol relying on the use of BEt3 together with lutidine hydrochloride has been described by Takahashi for the regeneration of Cp2TiCl from cyclizations involving /1-hydride elimination as the terminating step [83]. 

The above-mentioned results indicate the additive effect of protons. Actually, a catalytic process is formed by protonation of the metal-oxygen bond instead of silylation. 2,6-Lutidine hydrochloride or 2,4,6-collidine hydrochloride serves as a proton source in the Cp2TiCl2-catalyzed pinacol coupling of aromatic aldehydes in the presence of Mn as the stoichiometric reduc-tant [30]. Considering the pKa values, pyridinium hydrochlorides are likely to be an appropriate proton source. Protonation of the titanium-bound oxygen atom permits regeneration of the active catalyst. High diastereoselectivity is attained by this fast protonation. Furthermore, pyridine derivatives can be recovered simply by acid-base extraction or distillation. 

Symmetrical tetrachloropyridine is also the product of 3,5-lutidine or 3,5-lutidine hydrochloride chlorination at 260 °C117. 

Finally, Fuse et al. recently proposed the use of EtsB together with 2,6-lutidine hydrochloride or 2,4,6-collidine hydrochloride to improve the capacity of the system for regenerating titanocene(III) from Cp2Ti(Cl)H in the [Ti ]-catalyzed cyclization of 6,7-epoxygeranyl acetate [70]. 

Schrock has made Cp Me3M=N—N=MMe3Cp (M = Mo or W) where the back donation is so strong that the N2 is now effectively reduced to a hydrazide tetraanion, as shown by the N—N distance of 1.235 A (Mo). Ammonia is formed with lutidine hydrochloride as proton source and Zn/Hg as reductant. 

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