2-Propanephosphonic acid anhydride (T3P)-mediated segment coupling and head-to-tail cyclization of sterically hindered peptides

1999 ◽  
pp. 1847-1848 ◽  
Author(s):  
Jana Klose ◽  
Michael Bienert ◽  
Christoph Mollenkopf ◽  
Detlef Wehle ◽  
Chong-wu Zhang ◽  
...  
Keyword(s):  
Acid Anhydride ◽  
Sterically Hindered ◽  
Head To Tail Cyclization

Reactions of the Highly Sterically Hindered Silanols (Me3Si)3CSiMe(C6H4R-p)OH with acid chlorides

2003 ◽  
Vol 2003 (1) ◽  
pp. 38-39
Author(s):  
Kazem D. Safa ◽  
Hojjat Mostafaie ◽  
Yaghoub Haghighat Doust
Keyword(s):  
Acetic Acid ◽  
Acid Chloride ◽  
Acid Anhydride ◽  
Acid Chlorides ◽  
Sterically Hindered

The silanol TsiSiMe(C6H4Me- p)OH (Tsi = (Me3Si)3C) has been shown to react with some acid chlorides RCOCl (R = Me, Et, ClCH2) and acetic acid anhydride (MeCO)2O to give the related carboxylates TsiSiMe(C6H4Me- p)OCOR. It also reacts with 4-O2NC6H4COCl and a mixture of Cl2CHCOCl and AlCl3 to give TsiSiMe[C6H3-3-(CO-C6H4NO2-p)-4-Me]OCOC6H4NO2-p and TsiSiMe[C6H3-3-(COCHCl2- 4-Me)]OCOCHCl2 respectively. The reaction of the silanol TsiSiMe(C6H4OMe-p)OH with acid chloride RCOCl (R = Me or Et) gives TsiSiMeClOCOR and TsiSiMe(RCO)OCOR, while in the presence of pyridine gives the normal carboxylate TsiSiMe(C6H4OMe-p)OCOR.

Nickel-Catalyzed Regioselective Hydroalkylation of 1,3-Dienes with Hydrazones

2019 ◽  
Author(s):  
Leiyang Lv ◽  
Dianhu Zhu ◽  
Zihang Qiu ◽  
Jianbin Li ◽  
Chao-Jun Li
Keyword(s):  
Catalytic Method ◽  
Unsaturated Hydrocarbons ◽  
Carbon Nucleophiles ◽  
Aryl Aldehydes ◽  
Aldehydes And Ketones ◽  
Sterically Hindered

Hydroalkylation of unsaturated hydrocarbons with unstablized carbon nucleophiles is difficult and remains a major challenge. The disclosed examples so far mainly focused on the involvement of heteroatom and/or stabilized carbon nucleophiles as efficient reaction partners. Reported here is an unprecedented regioselective nickel-catalyzed hydroalkylation of 1,3-dienes with hydrazones, generated in situ from abundant aryl aldehydes and ketones and acted as both the sources of unstabilized carbanions and hydride. With this strategy, both terminal and sterically hindered internal dienes are hydroalkylated efficiently in a highly selective manner, thus providing a novel and reliable catalytic method to construct challenging C(sp3)-C(sp3) bonds.

Synthesis of Conjugated Triynes via Alkyne Metathesis

2019 ◽  
Author(s):  
Idriss Curbet ◽  
Sophie Colombel-Rouen ◽  
Romane Manguin ◽  
Anthony Clermont ◽  
Alexandre Quelhas ◽  
...  
Keyword(s):  
Steric Hindrance ◽  
High Selectivity ◽  
Alkyne Metathesis ◽  
Cross Metathesis ◽  
Synthetic Strategy ◽  
Sterically Hindered ◽  
Site Selective

<div> <div> <div> <div> <p>The synthesis of conjugated triynes by molybdenum-catalyzed alkyne metathesis is reported. Strategic to the success of this approach is the utilization of sterically-hindered diynes that allowed for the site- selective alkyne metathesis to produce the desired con- jugated triyne products. The steric hindrance of alkyne moiety was found to be crucial in preventing the for- mation of diyne byproducts. This novel synthetic strategy was amenable to self- and cross-metathesis providing straightforward access to the corresponding symmetrical and dissymmetrical triynes with high selectivity. </p> </div> </div> </div> </div>

scholarly journals Propylphosphonic acid anhydride–mediated amidation of Morita–Baylis–Hillman–derived indolizine-2-carboxylic acids

2021 ◽  
pp. 174751982098715
Author(s):  
Khethobole C Sekgota ◽  
Michelle Isaacs ◽  
Heinrich C Hoppe ◽  
Ronnett Seldon ◽  
Digby F Warner ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Carboxylic Acids ◽  
Coupling Agent ◽  
Methyl Esters ◽  
Acid Anhydride

Propylphosphonic acid anhydride has been successfully used as a coupling agent in the synthesis of a series of indolizine-2-carboxamido derivatives from indolizine-2-carboxylic acid and its 3-acetylated analogue. The acid substrates were obtained by saponification of the corresponding methyl esters produced, in turn, selectively and efficiently, by time-controlled cyclisation of a single Morita–Baylis–Hillman adduct. Various amino and hydrazino compounds with medicinal potential have been used to prepare indolizine-2-carboxamido and hydrazido derivatives.

Utilizing o-quinone methide chemistry: synthesis of sterically hindered acridin-4-ols

2021 ◽  
Vol 31 (2) ◽  
pp. 262-264
Author(s):  
Svetlana K. Polyakova ◽  
Tatyana V. Balashova ◽  
Roman V. Rumyantcev ◽  
Maxim V. Arsenyev ◽  
Georgy K. Fukin ◽  
...  
Keyword(s):  
Quinone Methide ◽  
Sterically Hindered

β,γ-trans-Selective γ-butyrolactone formation via homoenolate cross-annulation of enals and aldehydes catalyzed by sterically hindered N-heterocyclic carbene

Tetrahedron ◽  
2021 ◽  
pp. 132191
Author(s):  
Ryuji Kyan ◽  
Yuya Kitagawa ◽  
Ryuji Ide ◽  
Kohei Sato ◽  
Nobuyuki Mase ◽  
...  
Keyword(s):  
Sterically Hindered
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