Overcrowded aminophospanitrenes: a case study

2017 ◽  
Vol 72 (11) ◽  
pp. 865-871
Author(s):  
Jürgen Tirrée ◽  
Alexander V. Ruban ◽  
Martin Nieger ◽  
Claudia Li ◽  
László Nyulászi ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Ring Opening ◽  
Ring System ◽  
Thermally Induced ◽  
Induced Decomposition

AbstractIn a search for stable phosphinonitrenes generated by thermally induced decomposition of the azidophosphines 8a, b, different cyclodiphosp(V)azene products were generated. While in the case of 8a the expected phosphinonitrene dimer 10 could be obtained, from 8b, which has the sterically more demanding TMP substituents, product 11, was obtained and characterized. DFT calculations have revealed that the primarily formed phosphinonitrene 9b is unstable against loss of TMP˙, and the resulting radical dimerizes to the biradicaloid 1,3-diaza-2,4-diphosphetane-2,4-diyl 13. Compound 13 then dimerizes after ring opening, yielding in the ring system, which provides the final product upon reaction with the starting azidophosphine.

Reversible Oxidative-Addition and Reductive-Elimination of Thiophene from a Titanium Complex and Its Thermally-Induced Hydrodesulfurization Chemistry

2019 ◽  
Author(s):  
Alejandra Gomez-Torres ◽  
J. Rolando Aguilar-Calderón ◽  
Carlos Saucedo ◽  
Aldo Jordan ◽  
Alejandro J. Metta-Magaña ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Ring Opening ◽  
Thiophene Ring ◽  
Oxidative Addition ◽  
Reductive Elimination ◽  
Thermally Induced ◽  
Titanium Complex

<p>The masked Ti(II) synthon (<sup>Ket</sup>guan)(<i>η</i><sup>6</sup>-Im<sup>Dipp</sup>N)Ti (<b>1</b>) oxidatively adds across thiophene to give ring-opened (<sup>Ket</sup>guan)(Im<sup>Dipp</sup>N)Ti[<i>κ</i><sup>2</sup>-<i>S</i>(CH)<sub>3</sub><i>C</i>H] (<b>2</b>). Complex <b>2</b> is photosensitive, and upon exposure to light, reductively eliminates thiophene to regenerate <b>1</b> – a rare example of early-metal mediated oxidative-addition/reductive-elimination chemistry. DFT calculations indicate strong titanium π-backdonation to the thiophene π*-orbitals leads to the observed thiophene ring opening across titanium, while a proposed photoinduced LMCT promotes the reverse thiophene elimination from <b>2</b>. Finally, pressurizing solutions of <b>2 </b>with H<sub>2</sub> (150 psi) at 80 °C leads to the hydrodesulfurization of thiophene to give the Ti(IV) sulfide (<sup>Ket</sup>guan)(Im<sup>Dipp</sup>N)Ti(S) (<b>3</b>) and butane. </p>

2,5-Bridged 1-Carba-arachno-pentaborane(10) Derivatives – Intermediates on the Way to Pentaalkyl-1,5-dicarba-closo-pentaboranes(5)

2015 ◽  
Vol 70 (10) ◽  
pp. 741-745 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Hans-Joerg Schanz
Keyword(s):  
Nmr Spectroscopy ◽  
Low Temperature ◽  
Thermal Degradation ◽  
Dft Calculations ◽  
Large Excess ◽  
Thermally Induced ◽  
Independent Synthesis ◽  
Induced Decomposition ◽  
C Nmr

AbstractStimulated by a report from (R. Köster, G. Benedikt, M. A. Grassberger, Liebigs Ann. Chem. 1968, 719, 187.) on a carbaborane, for which the structure of 2,3,4,5,-tetraethlyl-1-methyl-2,5-μ-(ethyl-1′,1′-diyl)-1-carba-arachno-pentaborane(10) 1 was proposed, an independent synthesis was developed. Diethyl(ethynyl)borane was generated in situ in the presence of a large excess of “Et2B–H” (hydride bath) by ethynyl/H exchange, using ethynyl(trioctyl)tin to react in a mixture with diethyl(vinyl)borane at low temperature. Hydroboration and Et2B–H-catalysed condensation afforded 1, as shown by 11B, 13C NMR spectroscopy and DFT calculations. Thermal degradation of 1 gave 2,3,4-triethyl-1,5-dimethyl-1,5-dicarba-closo-pentaborane(5), whereas the pentaethyl-1,5-dicarba-closo-pentaborane(5) resulted from thermally induced decomposition of other suitably substituted arachno carbaboranes.

Reversible Oxidative-Addition and Reductive-Elimination of Thiophene from a Titanium Complex and Its Thermally-Induced Hydrodesulfurization Chemistry

2019 ◽  
Author(s):  
Alejandra Gomez-Torres ◽  
J. Rolando Aguilar-Calderón ◽  
Carlos Saucedo ◽  
Aldo Jordan ◽  
Alejandro J. Metta-Magaña ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Ring Opening ◽  
Thiophene Ring ◽  
Oxidative Addition ◽  
Reductive Elimination ◽  
Thermally Induced ◽  
Titanium Complex

<p>The masked Ti(II) synthon (<sup>Ket</sup>guan)(<i>η</i><sup>6</sup>-Im<sup>Dipp</sup>N)Ti (<b>1</b>) oxidatively adds across thiophene to give ring-opened (<sup>Ket</sup>guan)(Im<sup>Dipp</sup>N)Ti[<i>κ</i><sup>2</sup>-<i>S</i>(CH)<sub>3</sub><i>C</i>H] (<b>2</b>). Complex <b>2</b> is photosensitive, and upon exposure to light, reductively eliminates thiophene to regenerate <b>1</b> – a rare example of early-metal mediated oxidative-addition/reductive-elimination chemistry. DFT calculations indicate strong titanium π-backdonation to the thiophene π*-orbitals leads to the observed thiophene ring opening across titanium, while a proposed photoinduced LMCT promotes the reverse thiophene elimination from <b>2</b>. Finally, pressurizing solutions of <b>2 </b>with H<sub>2</sub> (150 psi) at 80 °C leads to the hydrodesulfurization of thiophene to give the Ti(IV) sulfide (<sup>Ket</sup>guan)(Im<sup>Dipp</sup>N)Ti(S) (<b>3</b>) and butane. </p>

Resolving the Mystery of Ring Opening in the Synthesis of Benzo[d][1, 3]oxazin-4-one and Quinazolin-4(3H)-one

2019 ◽  
Vol 16 (11) ◽  
pp. 898-905
Author(s):  
Harun Patel ◽  
Rahul Pawara ◽  
Sanjay Surana
Keyword(s):  
Characteristic Feature ◽  
Ring Opening ◽  
Biological Activities ◽  
Heterocyclic Ring ◽  
Ring System ◽  
Time Saving ◽  
Fusion Strategy ◽  
Good Template ◽  
Lead Generation

Quinazoline is the six-membered heterocyclic ring system reported for its versatile biological activities. This characteristic feature of quinazoline makes it a good template for a lead generation library. Ring opening is one of the major concerns in the synthesis of quinazolin-4(3H)-one that results in diamide formation. Here, alternative fusion strategy is reported, which is a time-saving and costeffective method to overcome the ring opening problem associated with the synthesis of benzo[ d][1,3]oxazin-4-one and quinazolin-4(3H)-one.

Some Transformations of Adducts of 3,6-Dimethoxy-4,5-methylenedioxy-1,2-didehydrobenzene and Furans. An Approach to the 5,8-Dimethoxy-6,7-methylenedioxynaphtho[2,3-c]furan-4,9-dione Ring System of Ventilone A

1998 ◽  
Vol 51 (5) ◽  
pp. 409 ◽  
Author(s):  
Jarrod H. Buttery ◽  
Dieter Wege
Keyword(s):  
Ring Opening ◽  
Ring System ◽  
Subsequent Oxidation ◽  
Naturally Occurring

Adducts derived from the aryne 3,6-dimethoxy-4,5-methylenedioxy-1,2-didehydrobenzene (19) with furan and 2-methoxyfuran have been converted into 5,8-dimethoxy-6,7-methylenedioxy-1,2-naphthoquinone (22) and 5,8-dimethoxy-6,7-methylenedioxy-1,4-naphthoquinone (24) respectively. The trapping of (19) with 1H,3H-furo[3,4-c]furan (38) yielded an unstable adduct (37), which on acid-catalysed ring opening and subsequent oxidation was transformed into 5,8-dimethoxy-6,7-methylenedioxynaphtho[2,3-c]furan-4,9-dione (36), a compound possessing the ring system of the naturally occurring quinone ventilone A.

Carbon–nitrogen bond cleavage of pyridine with two molecular substituted allenoates: access to 2-arylpyrimidin-4(3H)-one

2018 ◽  
Vol 54 (100) ◽  
pp. 14128-14131 ◽  
Author(s):  
Tao Jin ◽  
Hongdong Yuan ◽  
Shikuan Su ◽  
Xueshun Jia ◽  
Chunju Li ◽  
...  
Keyword(s):  
Benzene Ring ◽  
Ring Opening ◽  
Pyridine Ring ◽  
Bond Cleavage ◽  
Ring System ◽  
Nitrogen Bond

A DABCO-catalyzed annulation reaction of pyridin-2-amine and substituted allenoates enables the ring-opening of a pyridine ring system and the formation of two new rings including a pyrimidinone ring and a benzene ring.

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