One-electron oxidation of 3-substituted 2-oxa-3-azabicyclo[2.2.2]octane derivatives

Nelsen, Stephen F.; Thompson-Colon, James A.; Kirste, B.; Rosenhouse, A.; Kaftory, Menahem

doi:10.1021/ja00257a037

Cited by 18 publications

(9 citation statements)

References 1 publication

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“…(1R,4S)-enantiomer and racemic 14c: 1 H NMR (CHCl 3 ) and 13 C NMR (CHCl 3 ), same data as in Lit. 21 and Lit., 31 respectively.…”

Section: (-)-(3s6s)-3-methyl-36-dihydro-2h-12-oxazine-6-carboxylicmentioning

confidence: 98%

“…The racemic N-carbamates (±)-14c, 31 (±)-15b 28 and (±)-16b 28 as well as the cyclohexadiene adduct (±)-14a [32][33][34] are known compounds. The latter compound was prepared from the achiral nitroso dienophile 18 [32][33][34] ac-cording to the procedure which had been used for the synthesis of the chiral adducts, 18 reacted at a slower rate than 3b (2 weeks at -20°C).…”

Section: Preparation Of Racemic Compounds (Scheme 4)mentioning

confidence: 99%

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Enantioselective Diels-Alder Reaction with an α-Chloronitrose Dienophile Derived from 5-O-Acetyl-2,3-isopropylidenedioxy-d-ribose

Defoin¹,

Joubert²,

Heuchel³

et al. 2000

Synthesis

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Crystalline 5-O-acetyl-2,3-isopropylidenedioxy-D-ribonolactone oxime (8) was synthesised from D-ribose in 40% overall yield. The chloronitroso dienophile 3b was obtained from 8 by oxidation with t-BuOCl and underwent asymmetric Diels-Alder reaction with cyclic and acyclic dienes 10-13 to give crystalline adducts 14a-17a in good yield and excellent enantiomeric excess (93-99%).A. Defoin et al. PAPER Synthesis 2000, No. 12, 1719-1726 ISSN 0039-7881 © Thieme Stuttgart · New York rate was fast with cyclohexadiene (10) and slow (ca 1-2 d) with pentadienoic acid (11) and sorbic acid (12), leading to the corresponding chiral adducts 14a-16a as crystalline hydrochlorides in 75-86% yield (by direct precipitation with anhydrous diethyl ether). Hexa-2,4-diene (13) [ca 50:50 mixture of (E,E)-and (E,Z)-isomers 30 ] reacted rapidly with 3b and gave a mixture of the cis-adduct 17a and its trans-isomer (20%). The cis adduct 17a was isolated in 60% yield as a crystalline hydrochloride after aqueous extraction, as described by Kresze and Vasella. 20 Ribonolactone (9), which resulted from 3b, could be isolated from the organic phase. Scheme 2Benzyl (3S,6R)-3,6-Dimethyl-3,6-dihydro-2H-1,2-oxazine-2carboxylate (17b)To an aqueous solution of 17a (8 mL) [from aqueous extraction of the reaction mixture of 3b (0.82 mmol) and 13 (0.4 mL, 3.5 mmol, 2 equiv of (E,E)-diene)] was added dioxane (1 mL), NaHCO 3 (0.28 g, 3.4 mmol, 4 equiv) and ClCO 2 Bn (0.132 mL, 0.94 mmol, 1.2 equiv). The reaction mixture was stirred for 2 h at r.t., then extracted with Et 2 O (2 × 10 mL), the organic phase dried (MgSO 4 ) and evaporated. Purification by FC (CH 2 Cl 2 ) gave 17b (0.13 g, 63%) (as a mixture with 20% of trans-isomer); colorless resin.

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“…(1R,4S)-enantiomer and racemic 14c: 1 H NMR (CHCl 3 ) and 13 C NMR (CHCl 3 ), same data as in Lit. 21 and Lit., 31 respectively.…”

Section: (-)-(3s6s)-3-methyl-36-dihydro-2h-12-oxazine-6-carboxylicmentioning

confidence: 98%

Section: Preparation Of Racemic Compounds (Scheme 4)mentioning

confidence: 99%

Enantioselective Diels-Alder Reaction with an α-Chloronitrose Dienophile Derived from 5-O-Acetyl-2,3-isopropylidenedioxy-d-ribose

Defoin¹,

Joubert²,

Heuchel³

et al. 2000

Synthesis

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“…However, this conclusion is fundamentally incorrect (Nelsen et al, 1987), and the error can be traced to the rabbit-ear lone pair representation that was used. Similar analysis using the proper n (s) O and n (p) O lone pairs is shown in Fig.…”

Section: Does the Local Symmetry Of Inequivalent Lone Pairs Persist I...mentioning

confidence: 99%

Rabbit-ears hybrids, VSEPR sterics, and other orbital anachronisms

Clauss

Nelsen

Ayoub³

et al. 2014

Chem. Educ. Res. Pract.

Self Cite

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We describe the logical flaws, experimental contradictions, and unfortunate educational repercussions of common student misconceptions regarding the shapes and properties of lone pairs, inspired by overemphasis on “valence shell electron pair repulsion” (VSEPR) rationalizations in current freshman-level chemistry textbooks. VSEPR-style representations of orbital shape and size are shown to be fundamentally inconsistent with numerous lines of experimental and theoretical evidence, including quantum mechanical “symmetry” principles that are sometimes invoked in their defense. VSEPR-style conceptions thereby detract from more accurate introductory-level teaching of orbital hybridization and bonding principles, while also requiring wasteful “unlearning” as the student progresses to higher levels. We include specific suggestions for how VSEPR-style rationalizations of molecular structure can be replaced with more accurate conceptions of hybridization and its relationship to electronegativity and molecular geometry, in accordance both with Bent's rule and the consistent features of modern wavefunctions as exhibited by natural bond orbital (NBO) analysis.

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“…Correlation of electrochemical standard potential E°′ vs vertical ionization potential for a series of aromatic compounds that have been measured in acetonitrile solution, and extrapolation of the trend to several other prototypical molecules with ionization potentials that exceed 10 eV. 15,16 The electron transfer from the compounds within the blue box can occur through an outer sphere process, whereas the high ionization potential compounds can react only through an inner sphere electrocatalytic process because at the implied electrochemical potentials the solvent would undergo electron transfer in preference to the solute. between standard electrochemical potentials vs the vertical ionization potentials for a series of solution species.…”

Section: Introductionmentioning

confidence: 99%