Rules for ring closure: ring formation by conjugate addition of oxygen nucleophiles

1977 ◽  
Vol 42 (24) ◽  
pp. 3846-3852 ◽  
Author(s):  
Jack E. Baldwin ◽  
Richard C. Thomas ◽  
Lawrence I. Kruse ◽  
Lee Silberman
Keyword(s):  
Conjugate Addition ◽  
Ring Formation ◽  
Ring Closure

ChemInform Abstract: RULES FOR RING CLOSURE- RING FORMATION BY CONJUGATE ADDITION OF OXYGEN NUCLEOPHILES

1978 ◽  
Vol 9 (14) ◽  
Author(s):  
J. E. BALDWIN ◽  
R. C. THOMAS ◽  
L. I. KRUSE ◽  
L. SILBERMAN
Keyword(s):  
Conjugate Addition ◽  
Ring Formation ◽  
Ring Closure

A Convenient Route to O-Glycosyl Lactates via Conjugate Addition to 2-Nitroglycals: Ring Closure to Novel Pyrano[2.3-b][1,4]-oxazines

Synthesis ◽  
2003 ◽  
Vol 2004 (01) ◽  
pp. 53-58
Author(s):  
Richard Schmidt ◽  
Ahmed Khodair ◽  
Kandasamy Pachamuthu
Keyword(s):  
Conjugate Addition ◽  
Ring Closure ◽  
Convenient Route

scholarly journals Rho-dependent control of the Citron kinase, Sticky, drives midbody ring maturation

2019 ◽  
Vol 30 (17) ◽  
pp. 2185-2204 ◽  
Author(s):  
Nour El-amine ◽  
Sabrya C. Carim ◽  
Denise Wernike ◽  
Gilles R. X. Hickson
Keyword(s):  
Function Analysis ◽  
Mechanisms Of Action ◽  
Ring Formation ◽  
Ring Closure ◽  
S2 Cells ◽  
Contractile Ring ◽  
Subsequent Formation ◽  
Control Assembly ◽  
Citron Kinase ◽  
Guide Ring

Rho-dependent proteins control assembly of the cytokinetic contractile ring, yet it remains unclear how those proteins guide ring closure and how they promote subsequent formation of a stable midbody ring. Citron kinase is one important component required for midbody ring formation but its mechanisms of action and relationship with Rho are controversial. Here, we conduct a structure–function analysis of the Drosophila Citron kinase, Sticky, in Schneider’s S2 cells. We define two separable and redundant RhoGEF/Pebble-dependent inputs into Sticky recruitment to the nascent midbody ring and show that each input is subsequently required for retention at, and for the integrity of, the mature midbody ring. The first input is via an actomyosin-independent interaction between Sticky and Anillin, a key scaffold also required for midbody ring formation. The second input requires the Rho-binding domain of Sticky, whose boundaries we have defined. Collectively, these results show how midbody ring biogenesis depends on the coordinated actions of Sticky, Anillin, and Rho.

Conjugate addition approach for natural product synthesis inspired by gibberellin and solanoeclepin A targets

2013 ◽  
Vol 85 (6) ◽  
pp. 1149-1160 ◽  
Author(s):  
Minoru Isobe
Keyword(s):  
Oxygen Atom ◽  
Low Temperatures ◽  
Bond Formation ◽  
Conjugate Addition ◽  
Ring Closure ◽  
Natural Product Synthesis ◽  
Partial Synthesis ◽  
Unsaturated Ketones ◽  
Cyclobutane Ring ◽  
Zinc Enolate

Trimethylzincate is known to react through conjugate addition to α,β-unsaturated ketones, but adds much faster to α,β-unsaturated esters at low temperatures. Since the intermediate zinc enolate behaves differently from that of dimethylcuprate, it offers scope for application in a partial synthesis of gibberellin A3. A second example involving vinylsulfones having an oxygen atom on the γ-carbon strongly directs incoming nucleophiles in conjugate addition mode. Heteroatom-directed conjugate addition (HADCA) provides very reactive carbanion intermediates leading to cyclobutane ring formation, necessary for synthesis of solanoeclepin A. An alternative reaction for the four-membered carbocyclic ring closure was explored to make a bond formation between the propargylic cation of Nicholas type and allyltrimethylsilane nucleophile of Hosomi–Sakurai type. This method allowed a formation of tricyclo[5.2.1.01,6]decene framework.

New Six- to Eight-Membered-Ring Formation Based on the lntramolecular Endo-Mode Ring Closure of Allenyl (Substituted Phenyl)alkyl Ketones

1994 ◽  
Vol 23 (3) ◽  
pp. 597-600 ◽  
Author(s):  
Yoshimitsu Nagao ◽  
Woo Song Lee ◽  
Yoichi Komaki ◽  
Shigeki Sano ◽  
Motoo Shiro
Keyword(s):  
Membered Ring ◽  
Ring Formation ◽  
Ring Closure

Carbocyclic Construction: The Deng Synthesis of (-)-Plicatic Acid

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Brefeldin A ◽  
Conjugate Addition ◽  
Oxidative Cyclization ◽  
Ring Closure ◽  
Silyl Ether ◽  
University Of Pittsburgh ◽  
University Of Wisconsin ◽  
Institute Of Technology ◽  
The University ◽  
Academy Of Sciences

Tehshik P. Yoon of the University of Wisconsin uncovered (J. Am. Chem. Soc. 2009, 131, 14604) conditions for the crossed photodimerization of acyclic enones. Minoru Isobe of Nagoya University extended (Synlett 2009, 1157) conjugate addition–intramolecular epoxide opening to substrates such as 4, leading to the cyclobutane 6 with high diastereocontrol. In the course of a total synthesis of (+)-brefeldin A, Jinsung Tae of Yonsei University established (Synlett 2009, 1303) conditions for the trans-selective cyclization of 7 to 8. Cyclization with TiCl4 gave the alternative cis diastereomer. Several methods have been put forward for the conversion of carbohydrate derivatives to carbocycles. Yeun-Mi Tsai of the National Taiwan University found (Tetrahedron Lett . 2009, 50, 3805) that acyl silanes such as 9 cyclized efficiently under free radical conditions, leading to the silyl ether 10. Tanmaya Pathak of the Indian Institute of Technology, Kharagpur, developed (Eur. J. Org. Chem. 2009, 872) the tandem conjugate addition– intramolecular alkylation conversion of 11 to 13. Slawomir Jarosz of the Polish Academy of Sciences, Warsawza, observed (Heterocycles 2009, 80, 1303) that the oxime derived from 14 cyclized to 15. The cyclization was accelerated by high pressure. Cyclohexanes can also be prepared from carbohydrates. Tony K. M. Shing of the Chinese University of Hong Kong showed (Organic. Lett. 2009, 11, 5070) that the nitrile oxide derived from 16 cyclized to 17, that he carried on to (-)-gabosine O. John K. Gallos of the Aristotle University of Thessaloniki described (Tetrahedron Lett. 2009, 50, 6916) related work. Paul E. Floreancig of the University of Pittsburgh devised (Organic. Lett. 2009, 11, 3152) conditions for the oxidative cyclization of 18 to 19. Ring closure proceeded with high equatorial selectivity. Kou Hiroya of Tohoku University found (J. Org. Chem. 2009, 74, 6623) that the single oxygenated stereogenic center of 20 directed the dissolving metal reduction–enolate trapping, leading to 21. Similarly, Susumu Kobayashi of the Tokyo University of Science showed (Synlett 2009, 1605) that the oxygenated stereogenic centers of 22 set the alkylated centers of 23. Many marine organisms are able to carry out brominative and chlorinative polyolefin cyclizations.

scholarly journals Accessing simply-substituted 4-hydroxytetrahydroisoquinolines via Pomeranz–Fritsch–Bobbitt reaction with non-activated and moderately-activated systems

2017 ◽  
Vol 13 ◽  
pp. 1871-1878 ◽  
Author(s):  
Marco Mottinelli ◽  
Mathew P Leese ◽  
Barry V L Potter
Keyword(s):  
Medicinal Chemistry ◽  
Ring Formation ◽  
Ring Closure ◽  
Reductive Alkylation ◽  
One Pot ◽  
Double Ring ◽  
Mineral Acids ◽  
Reaction Concentration ◽  
Aromatic Systems ◽  
The Right

Background: 1,2,3,4-Tetrahydroisoquinolines (THIQs) are common motifs in alkaloids and in medicinal chemistry. Synthetic access to THIQs via the Pomeranz–Fritsch–Bobbit (PFB) methodology using mineral acids for deactivated, electron-poor aromatic systems, is scarcely represented in the literature. Here, the factors controlling the regiochemical outcome of cyclization are evaluated. Results: A double reductive alkylation was telescoped into a one-pot reaction delivering good to excellent yields of desired aminoacetals for cyclization. Cyclization of activated systems proceeded smoothly under standard PFB conditions, but for non-activated systems the use of HClO4 alone was effective. When cyclization was possible in both para- and ortho-positions to the substituent, 7-substituted derivatives were formed with significant amounts of 5-substituted byproduct. The formation of the 4-hydroxy-THIQs vs the 4-methoxy-THIQ products could be controlled through modification of the reaction concentration. In addition, while a highly-activated system exclusively cyclized to the indole, this seems generally highly disfavored. When competition between 6- and 7-ring formation was investigated in non-activated systems, 5,7,8,13-tetrahydro-6,13-methanodibenzo[c,f]azonine was exclusively obtained. Furthermore, selective ring closure in the para-position could be achieved under standard PFB conditions, while a double ring closure could be obtained utilizing HClO4. Conclusion: Reactivity differences in aminoacetal precursors can be employed to control cyclization using the PFB methodology. It is now possible to select confidently the right conditions for the synthesis of N-aryl-4-hydroxy-1,2,3,4-tetrahydroisoquinolines.

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