scholarly journals Oxidative Functionalization of Trinor-18α-olean-17(22)-ene Derivatives. Annulation of the E-Ring by an Intramolecular Aldol Reaction

2021 ◽  
Author(s):  
Kinga Kuczynska ◽  
Jarosław Jaźwiński ◽  
Zbigniew Pakulski ◽  
Piotr Cmoch ◽  
Roman Luboradzki
Keyword(s):  
Aldol Reaction ◽  
Oxidative Functionalization

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

Mukaiyama Aldol Reaction Catalyzed by (Benz)imidazolium-Based Halogen Bond Donors

2020 ◽  
Author(s):  
Revannath L. Sutar ◽  
Nikita Erochok ◽  
Stefan Huber
Keyword(s):  
Halogen Bond ◽  
Aldol Reaction ◽  
Mukaiyama Aldol Reaction ◽  
Mukaiyama Aldol ◽  
Background Reaction ◽  
Strong Performance ◽  
The Stability ◽  
Elemental Iodine

A series of cationic monodentate and bidentate iodo(benz)­imidazolium-based halogen bond (XB) donors were employed as catalysts in a Mukaiyama aldol reaction. While 5 mol% of a monodentate variant showed noticeable activity, a <i>syn</i>-preorganized bidentate XB donor provided a strong performance even with 0.5 mol% loading. In contrast to the very active BAr<sup>F</sup><sub>4</sub> salts, PF<sub>6</sub> or OTf salts were either inactive or showed background reaction. Repetition experiments clearly ruled out a potential hidden catalysis by elemental iodine and demonstrated the stability of our catalyst over three consecutive cycles.

Synthesis of the C19–C30 Bis-THF Fragment of Iriomoteolide-13a via Stepwise SN2 Cyclization and Intramolecular syn-Oxypalladation

2020 ◽  
Author(s):  
Hui Zhao ◽  
Kai Gao ◽  
Haichen Ma ◽  
Tsz Chun Yip ◽  
Wei-Min Dai
Keyword(s):  
Aldol Reaction ◽  
Allylic Alcohol ◽  
Asymmetric Dihydroxylation ◽  
Hydroxy Groups

The C19–C30 bis-THF fragment of the proposed structure of iriomoteolide-13a has been synthesized. The w-mesyloxy-substituted stereotetrad possessing three continuous hydroxy groups was generated by <i>anti</i>-aldol reaction and asymmetric dihydroxylation (AD). Upon heating in pyridine the stereotetrad underwent an S<sub>N</sub>2 cyclization to form the C19–C22 THF ring. It was followed by an intramolecular <i>syn</i>-oxypalladation of the C28 chiral allylic alcohol to give the C23–C26 THF ring.

Formal Total Syntheses of Crocacin A-D

2005 ◽  
Vol 70 (10) ◽  
pp. 1696-1708 ◽  
Author(s):  
Magnus Besev ◽  
Christof Brehm ◽  
Alois Fürstner
Keyword(s):  
Natural Products ◽  
Aldol Reaction ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Total Syntheses ◽  
Cross Coupling Reactions ◽  
Palladium Catalyzed ◽  
The Common ◽  
Selective Addition

A concise route to the common polyketide fragment5of crocacin A-D (1-4) is presented which has previously been converted into all members of this fungicidal and cytotoxic family of dipeptidic natural products by various means. Our synthesis features asyn-selective titanium aldol reaction controlled by a valinol-derived auxiliary, a zinc-mediated, palladium-catalyzedanti-selective addition of propargyl mesylate10to the chiral aldehyde9, as well as a comparison of palladium-catalyzed Stille and Suzuki cross-coupling reactions for the formation of the diene moiety of the target.

ChemInform Abstract: Asymmetric Aldol Reaction of Dichloroacetaldehyde Catalyzed by Diarylprolinol.

ChemInform ◽  
2016 ◽  
Vol 47 (49) ◽  
Author(s):  
Yujiro Hayashi ◽  
Daichi Nakamura ◽  
Yusuke Yasui ◽  
Kotaro Iwasaki ◽  
Hiroaki Chiba
Keyword(s):  
Aldol Reaction ◽  
Asymmetric Aldol ◽  
Asymmetric Aldol Reaction
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