ChemInform Abstract: SYNTHESES WITH ANHYDRO SUGARS. XXXI. PREPARATION OF 2-AMINO-1,6-ANHYDRO-2-DEOXY-β-D-MANNOPYRANOSE BY INTRAMOLECULAR SUBSTITUTION OF THE TOSYLOXY GROUP IN STERICALLY HINDERED POSITION OF 1,6-ANHYDRO-2-O-(P-TOLYLSULFONYL)-β-D-GLUCOPYRAN

1980 ◽  
Vol 11 (41) ◽  
Author(s):  
M. CERNY ◽  
H. VECERKOVA ◽  
I. CERNY ◽  
J. PACAK
Keyword(s):  
Sterically Hindered ◽  
Intramolecular Substitution

Preparation of 2-amino-1,6-anhydro-2-deoxy-β-D-mannopyranose by intramolecular substitution of the tosyloxy group in sterically hindered position of 1,6-anhydro-2-O-p-tolylsulfonyl-β-D-glucopyranose

1980 ◽  
Vol 45 (6) ◽  
pp. 1837-1844 ◽  
Author(s):  
Miloslav Černý ◽  
Hana Večerková ◽  
Ivan Černý ◽  
Josef Pacák
Keyword(s):  
Hydrochloric Acid ◽  
Tert Butanol ◽  
Sterically Hindered ◽  
Intramolecular Substitution

1,6 : 3,4-Dianhydro-2-O-p-tolylsulfonyl-β-D-galactopyranose (I) was converted to 1,6-anhydro-4-O-benzyl-2-O-p-tolylsulfonyl-β-D-glucopyranose (II) and then reacted with benzylisocyanate to give 3-O-(N-benzylcarbamoyl) derivative III. The cyclization of this substance under the effect of potassium tert-butoxide in tert-butanol gave 3-benzyl-(1,6-anhydro-4-O-benzyl-2,3-dideoxy-β-D-mannopyrano) [2,3-d]oxazolidin-2-one (IV) which was hydrolysed to 1,6-anhydro-4-O-benzyl-2-benzylamino-2-deoxy-β-D-mannopyranose (VIII). Catalytic debenzylation of VIII on palladium on charcoal in the presence of hydrochloric acid gave the hydrochloride of 2-amino-1,6-anhydro-2-deoxy-β-D-mannopyranose (IX), which was acetylated to triacetate XI. Depending on the conditions during catalytic debenzylation of the oxazolidine derivative IV either O-debenzylated derivative VI alone was obtained, or the completely debenzylated oxazolidine derivative VII.

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>

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

New sterically hindered bis-catechol, bis- o -quinone and its bis-triphenylantimony(v) bis-catecholate. 3,5-Di- tert -butyl-6-methoxymethylcatechol as alkylating agent

2018 ◽  
Vol 28 (1) ◽  
pp. 76-78 ◽  
Author(s):  
Maxim V. Arsenyev ◽  
Tatyana V. Astafeva ◽  
Evgeny V. Baranov ◽  
Andrey I. Poddelsky ◽  
Sergey A. Chesnokov
Keyword(s):  
Alkylating Agent ◽  
Tert Butyl ◽  
Sterically Hindered
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