Ring-opening hydrogenolysis

RING OPENING, HYDROGENOLYSIS AND DESULFURIZATION OF THIOPHENES BY METAL COMPLEXES. 

Stoichiometric ring opening, hydrogenolysis, and desulfurization of thiophenes... 

RING OPENING, HYDROGENOLYSIS AND DESULFURIZATION OF THIOPHENES BY METAL COMPLEXES Ring-opening reactions leading to t1 C,S thiophene-inserted metal complexes. 

I.2.2. Reduction with Ring Opening Hydrogenolysis with Raney Nickel... 

Scheme 1.1 Ring-opening hydrogenolysis of epoxides catalyzed by PdNPs (2nm) microencapsulated in polyurea. Recycling experiments can be carried out at least ten times with 97-99% yield. (Ref. [14a], Yu group, Org. Lett. 2003, 4665).

Of course, this analysis does not take into account any thermodynamic or kinetic limitations of the processes and neglects all the possible side reactions, while considering only the ring-opening (hydrogenolysis) reaction. On the other hand, this pattern does not take into account the steric hindrances for hydrogenolysis of external... 

Spectra obtained by 1H NMR allowed the progress of the hydrogenolysis reaction to be followed quantitatively. The cyclopropyl protons in the polymer have an 1H NMR peak at 61.0 ppm, while the protons on the ring-opened, gem-dimethyl repeat unit (Equation A) have an XH NMR peak at 61.35 ppm. The gem-dimethyl peak assignment was based on chemical shift calculations (17). Also the dimethyl acetal of acetone has protons in a similar chemical environment to those on the gem-dimethyl ketal repeat unit and they have a chemical shift between 61.3 ppm and 61.A ppm (18). A proton NMR spectrum of partially hydrogenated polycyclopropanone is shown in Figure 7. 

Ring opening polymerization can also be catalyzed by transition metals as shown in reaction (13) (12,30). The process appears to involve hydrogenolysis of the Si-N bond, given that reaction (13)... 

However, there is no reason to believe that a x-allyl or x-olefin mechanism for C—C bond rupture is limited to ring opening. Rather it should be a general process occurring in straight and branch-chain aliphatics as well. For the purpose of illustration, we write reactions (22) and (23) as generalizations of the reverse of (11) and (13), respectively. We shall refer to mechanisms such as (22) and (23) x-olefin/allyl hydrogenolysis... 

Fig. 14 Hydrogenolysis on metal catalysts product from ring opening reactions of Cl ring contraction compounds and their corresponding research octane number and motor octane number. Adapted from ref. 100.

---