5747-07-9Relevant academic research and scientific papers
Regio- and stereochemical studies on the nitroso-diels-alder reaction with 1,2-disubstituted dienes
Galvani, Gilles,Lett, Robert,Kouklovsky, Cyrille
, p. 15604 - 15614 (2013)
The regioselectivity of the nitroso-Diels-Alder reaction between unsymmetrical acyclic dienes and Boc-nitroso (Boc=tert-butoxycarbonyl) reagent or the Wightman chiral chloronitroso reagents has been studied. With the Boc-nitroso reagent, the selectivity is a consequence of steric effects at the C1-position in the diene and electronic effects at the C2-position in the diene. The combination of an unprotected hydroxyethyl side chain at C1 and an electron-withdrawing group at C2 allows complete regioselectivity in favour of the proximal isomer. The same isomer was obtained exclusively with the chiral nitroso reagent with high enantioselectivities. A model based on steric effects is proposed. Get selective! A combination of steric and electronic effects allows the design of 1,2-disubstituted dienes for highly regioselective nitroso-Diels-Alder reactions with either Boc-nitroso reagent or a chiral chloronitroso reagent. Enantiomerically enriched functionalized cycloadducts could be obtained by asymmetric and regioselective cycloadditions (see scheme; Boc=tert-butoxycarbonyl, TBS=tert-butyldimethylsilyl, Piv=pivaloyl). Copyright
Palladium-Promoted Neutral 1,4-Brook Rearrangement/Intramolecular Allylic Cyclization Cascade Reaction: A Strategy for the Construction of Vinyl Cyclobutanols
Zhang, Hao,Ma, Shiqiang,Yuan, Ziyun,Chen, Peng,Xie, Xingang,Wang, Xiaolei,She, Xuegong
, p. 3478 - 3481 (2017/07/15)
A cascade reaction to build vinyl cyclobutanol rings through activation of vinyl epoxides by palladium, followed by 1,4-Brook rearrangement and intramolecular cyclization with a palladium complex of the resulting carbon anion, is described. Through this cascade reaction, several highly substituted cyclobutanol substrates were achieved in good yields with high stereoselectivities.
Enantioselective Intermolecular Addition of Aliphatic Amines to Acyclic Dienes with a Pd-PHOX Catalyst
Adamson, Nathan J.,Hull, Ethan,Malcolmson, Steven J.
supporting information, p. 7180 - 7183 (2017/06/05)
We report a method for the catalytic, enantioselective intermolecular addition of aliphatic amines to acyclic 1,3-dienes. In most cases, reactions proceed efficiently at or below room temperature in the presence of 5 mol % of a Pd catalyst bearing a PHOX ligand, generating allylic amines in up to 97:3 er. The presence of an electron-deficient phosphine within the ligand not only leads to a more active catalyst but also is critical for achieving high site selectivity in the transformation.
Intramolecular [1 + 4 + 1] cycloaddition: Establishment of the method
Taber, Douglass F.,Guo, Pengfei,Guo, Na
supporting information; experimental part, p. 11179 - 11182 (2010/10/04)
Structurally complex and physiologically active natural products often include bicyclic and polycyclic ring systems having defined relative and absolute configuration. Approaches that allow the construction of more than one carbocyclic ring at a time have proven valuable, in particular those that allow at the same time the control of an array of new stereogenic centers. One of the most general and most widely used protocols has been the intramolecular Diels-Alder [4 + 2] cycloaddition, in which a single stereogenic center between the diene and the dienophile can control the relative and absolute configuration of the product. We report a two-step [1 + 4 + 1] procedure for bicyclic and polycyclic construction, based on the cyclization of an ω-dienyl ketone. This is complementary to, and will likely be as useful as, the intramolecular Diels-Alder cycloaddition.
Substituted fused bicyclic amines as modulators of chemokine receptor activity
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Page/Page column 21-22, (2010/02/13)
The present application describes modulators of CCR3 of formula (Ia) and (Ib): or pharmaceutically acceptable salt forms thereof, wherein Z, R1, R2, R3, R4, R5, R5′, R6, a, b, c, d, and u are as defined herein. In addition, methods of treating and preventing inflammatory diseases such as asthma and allergic diseases, as well as autoimmune pathologies such as rheumatoid arthritis and atherosclerosis using said modulators are disclosed.
Pentadienyl type lithium and potassium species: The regioselectivity of their reactions with electrophiles
Schlosser,Zellner,Leroux
, p. 1830 - 1836 (2007/10/03)
Seven structurally distinct pentadienyl type lithium and potassium compounds were screened against a variety of electrophiles in order to assess the regioselectivity of the trapping reactions. Organoborates and analogs thereof (fluorodimethoxyborane) proved to be perfectly regioreliable attacking only unsubstituted terminal positions and thus providing, after oxidation, exclusively primary allylic alcohols. 2,4-Pentadienyllithiums or -potassiums, that carry a methyl group at the 1- or 3-position, exhibit the same extreme regioselectivity towards halotrialkylsilanes or carbon dioxide. Although the unsubstituted parent compounds combine with such electrophiles still preferentially at the terminal position, considerable proportions of branched products are concomitantly formed as well (1/3-attack ratios ranging from 2:1 to >20:1). Hydroxyalkylating and alkylating reagents such as formaldehyde, oxirane or butyl iodide invariably afford regioisomeric mixtures generally varying in composition between 3:1 and 1:3. The condensation reaction with halotrialkylsilanes appears to follow a concerted (SN2-like) rather than an addition/elimination (ate complex-mediated) mechanism.
SYNTHESIS OF SORBIC ALCOHOL (2E,4E-HEXADIEN-1-OL)
Vasil'ev, A. A.,Poddubnaya, S. S.,Cherkaev, G. V.,Cherkaev, V. G.
, p. 1457 - 1460 (2007/10/02)
The decomposition of 1-acetoxy-3-acetoxymethoxy-4-hexene by the action of acids leads to a 1:2 mixture of 1-acetoxy-2,4-hexadiene and 1-acetoxy-3,5-hexadiene.The same compounds are formed in a ratio of 1:1 during the pyrolysis of 1,3-diacetoxy-4-hexene.
β-Halogeno Ether Synthesis of Olefinic Alcohols: Stereochemistry of the Ring-scission of 2-Substituted 3-Halogenotetrahydro-pyrans and -furans
Crombie, Leslie,Wyvill, Robert D.
, p. 1983 - 1996 (2007/10/02)
The stereochemical outcome of the sodium ring-scission of 2-substituted 3-halogenotetrahydro-pyrans and -furans, with 2-substitution represented by alkyl, alkenyl or aryl, is presented.Although the cis- and the trans-tetrahydropyran scissions are hyghly stereoselective for (E)-5-substituted pent-4-enol, this stereoselectivity breaks down when the 2-substituent is conformationally undiscriminating (deuterium) or has substantial anomeric effects (methoxy).Consideration of this, along with conformational data from the preceding paper, provides an explanation of the stereoselectivity of the tetrahydropyran scission.Evidence against a radical, and for a carbanion intermediate is presented and a common, very rapidly inverting, 3-carbanion is considered to be formed from either cis- or trans-stereoisomers.Ring scission is also rapid (the carbanion cannot be trapped), but less rapid than carbanion inversion, and takes place before the slower conformational inversion can occur so that the (E)/(Z)-nature of the unsaturated alcohol produced is controlled by the initial tetrahydropyran conformation.The unstereospecific nature of the ring scission of both cis- and trans-2-alkyl-3-chlorotetrahydrofurans is explained as a consequence of their existence in conformational equilibria. The high stereoselectivity of the ring scission of cis- and trans-3-chloro-2,3-dimethyltetrahydropyrans, and the poor stereoselectivity of the scission of 2-alkyl-3-chloro-2-methyltetrahydrpyrans, is explained; the reaction of sodium with 2-butyl-3,3-dichlorotetrahydropyran is considered.Using the ring-scission of 3-chlor-2-ethyltetrahydropyran, short syntheses of (+/-)-endo-brevicomin are described to illustrate the utility of β-halogen ether synthesis.
