ipso-Nitration of tert-butyl[n.2]metacyclophanes; through-space electronic interactions between two benzene rings

1998 ◽  
Vol 76 (7) ◽  
pp. 997-1005 ◽  
Author(s):  
Takehiko Yamato ◽  
Hideo Kamimura ◽  
Hirohisa Tsuzuki
Keyword(s):  
Electronic Interaction ◽  
Reaction Conditions ◽  
Electronic Interactions ◽  
Face To Face ◽  
Tert Butyl ◽  
Anti Conformer ◽  
Nitration Product ◽  
Group A ◽  
Fuming Nitric Acid ◽  
Methoxy Substituent

The selective introduction of one or two nitro groups by direct replacement of tert-butyl groups via the ipso aromatic nitration of the meta-bridged aromatic compounds having two arene rings is described. The ipso-nitration at the tert-butyl groups of syn- and anti-di-tert-butyl-dimethoxy[n.2]metacyclophanes 1 is attributed to the highly activated character of the aryl ring and the increased stabilization of a σ-complex intermediate arising from the dienone-type σ-complex intermediate possible in the case of an internally methoxy substituent. However, only one tert-butyl group is ipso-nitrated in the mild reaction conditions such as copper(II) nitrate in an acetic anhydride solution because of deactivation of the second aromatic ring by the introduced nitro group. A first σ-complex intermediate would be stabilized by two types of the through-space electronic interaction, i.e., face-to-face overlapping and intra-annular interaction with the opposing benzene ring, thus accelerating the reaction. The higher yields of mononitrated product are obtained in syn-conformer than in anti-conformer. Therefore, face-to-face overlapping might be much more favourable to stabilize the first σ-complex intermediate than the intra-annular interaction. On the other hand, nitration of 1 with fuming nitric acid afforded the two-fold ipso-nitration product 3 in quantitative yield. Thus, the number of ipso-nitration at the tert-butyl groups of 1 was strongly affected by the reactivity of the nitration reagent.Key words: cyclophanes, electrophilic aromatic substitutions, ipso-nitration, σ-complex intermediates, through-space electronic interactions.

Medium-sized cyclophanes, part 59:1 Nitration of [3.3]- and [3.3.3]metacyclophanes — Through-space electronic interactions between two or three benzene rings

2002 ◽  
Vol 80 (2) ◽  
pp. 207-215 ◽  
Author(s):  
Takehiko Yamato ◽  
Koji Tsuchihashi ◽  
Noriko Nakamura ◽  
Mai Hirahara ◽  
Hirohisa Tsuzuki
Keyword(s):  
Acetic Anhydride ◽  
Electronic Interaction ◽  
Reaction Conditions ◽  
Tert Butyl ◽  
Mixed Acid ◽  
Butyl Group ◽  
Tert Butyl Group ◽  
Starting Compound ◽  
Nitration Product ◽  
Fuming Nitric Acid

The two tert-butyl groups of anti-6,15-di-tert-butyl-9,18-dimethoxy[3.3]metacyclophane (anti-4) are both ipso-nitrated even under mild reaction conditions such as copper(II) nitrate in an acetic anhydride solution because of the decreased deactivation of the second aromatic ring by the introduced nitro group. On the other hand, anti-5,13-di-tert-butyl-8,16-dimethoxy[2.2]metacyclophane (anti-1) undergoes replacement of only one tert-butyl group under the same reaction conditions. The higher yields of the twofold ipso-nitration product anti-7 were obtained in nitration of anti-4 with fuming nitric acid or mixed acid (HNO3–H2SO4). Thus, the number of ipso-nitrations at the tert-butyl groups of anti-4 was strongly affected by the reactivity of the nitration reagent. Nitration of the corresponding syn-conformer syn-4 with copper(II) nitrate in an acetic anhydride solution, however, led only to the recovery of the starting compound. The presently developed procedure was further applied to the direct removal of the tert-butyl group by electrophilic substitution of the larger-sized ring macrocyclic metacyclophanes, cone- and partial-cone-tri-tert-butyl[3.3.3]metacyclophanes 11.Key words: [3n]metacyclophanes, conformation, ipso-nitration, through-space electronic interaction, crystal structure.

Medium-sized cyclophanes. Part 62:1 Formylation of anti-[n.2]metacyclophanes — Through-space electronic interactions between two benzene rings

2003 ◽  
Vol 81 (3) ◽  
pp. 244-252 ◽  
Author(s):  
Takehiko Yamato ◽  
Tsuyoshi Furukawa ◽  
Kan Tanaka ◽  
Tsutomu Ishi-i ◽  
Masashi Tashiro
Keyword(s):  
Methyl Ether ◽  
Electrophilic Aromatic Substitution ◽  
Similar Reaction ◽  
Reaction Conditions ◽  
Ring Inversion ◽  
Electronic Interactions ◽  
Strained Molecules ◽  
Tert Butyl ◽  
Butyl Group ◽  
Tert Butyl Group

Formylation of anti-[n.2]metacyclophanes (1) (n = 2, 3, 4) with dichloromethyl methyl ether in the presence of TiCl4 occurred selectively at para-position to the internal methyl substituents of anti-[n.2]metacyclophanes. Similar reaction of anti-5,13-di-tert-butyl-8,16-dimethyl[2.2]metacyclophane (6a) with dichloromethyl methyl ether in the presence of TiCl4 led to ipso-formylation at the tert-butyl group to give anti-5-tert-butyl-13-formyl-8,16-dimethyl[2.2]-meta cyclophane (7a) as well as the corresponding 2,7-di-tert-butyl-trans-10b,10c-dimethyl-10b,10c-dihydropyrene (10), anti-5-tert-butyl-8,16-dimethyl-13-(3-methyl-1-butene-2-yl)[2.2]metacyclophane (8), and anti-5,13-di-tert-butyl-exo-1-hydroxy-8,16-dimethyl[2.2]metacyclophane (9) depending on the reaction conditions. The higher yield of ipso-formylated product is obtained in the presence of AlCl3 MeNO2 in 80% yield along with anti-5-tert-butyl-8,16-dimethyl-13-(3-methyl-1-butene-2-yl)[2.2]metacyclophane (13). Thus, the yield of ipso-formylation at the tert-butyl group of 6a was strongly affected by the activity of the formylation catalyst. Interestingly, in the formylation of anti-6,14-di-tert-butyl-9,17-dimethyl[3.2]metacyclophane (6b) under the same reaction conditions, syn-6,14-di-tert-butyl-7-formyl-9,17-dimethyl[3.2]metacyclophane (14b) was obtained in 40% yield arising from the anti-syn-ring inversion of the formylation intermediate along with ipso-formylation product 7b in 42% yield. In the formylation of anti-[4.2] meta cyclophane (6c) only the mono-ipso-formylated product 7c was obtained in 92% yield. The formation of a two-fold ipso-formation product, i.e., anti-5,13-diformyl-8,16-dimethyl[2.2]metacyclophane (3a), was not observed under the reaction conditions used. The mechanism of the ipso-formation as well as the formation of the present novel reaction products 8 and 9 is also discussed. Key words: cyclophanes, strained molecules, electrophilic aromatic substitution, ipso-formylation, σ-complex intermediates, through-space electronic interactions.

Medium-sized cyclophanes. part 51. Acylation of [2.2]metaparacyclophanes: through-space electronic interactions between two benzene rings

2000 ◽  
Vol 78 (2) ◽  
pp. 238-247 ◽  
Author(s):  
Takehiko Yamato ◽  
Kiwamu Tokuhisa ◽  
Hirohisa Tsuzuki
Keyword(s):  
Benzene Ring ◽  
Acetyl Chloride ◽  
Electrophilic Aromatic Substitution ◽  
Electronic Interaction ◽  
Aromatic Substitution ◽  
Reaction Conditions ◽  
Tert Butyl ◽  
Butyl Group ◽  
Tert Butyl Group ◽  
Sigma Complex

The acylation of 8-methyl- (1b) and 8-methoxy[2.2]metaparacyclophane 1c with 1.1 equiv. of acetyl chloride in CS2 solution in the presence of aluminum chloride afforded 15-acetyl-8-methyl- (2b) and 12-acetyl-8-methoxy[2.2]metaparacyclophanes (3c) with 65 and 41% yields, respectively. The different orientations for the electrophilic substitution were observed to be dependant on the substituent at the 8 position. On the other hand, when the same reaction was carried out under the same reaction conditions with the corresponding 5-tert-butyl derivatives (11), ipso-acetylation at the tert-butyl group was observed along with acetylation on the para-benzene ring. The substituent effect on the 8-position was also observed in the present ipso-acetylation. The ipso-acylation at the tert-butyl group of 5-tert-butyl-8-methoxy[2.2]metaparacyclophane (11c) is attributed to the highly activated character of the aryl ring and the increased stabilization of a sigma-complex intermediate arising from the dienone-type sigma-complex intermediate possible in the case of a internal methoxy substituent. However, the present ipso-acetylation has not been observed in mild reaction conditions such as acetyl chloride in the presence of TiCl4 catalyst due to deactivation of the second aromatic ring by the introduced acetyl group on the para-benzene ring. The mechanism of these novel reactions is also discussed.Key words: cyclophanes, electrophilic aromatic substitution, regioselectivity, through-space electronic interaction, ipso-acylation.

N-Chlorinative Ring Contraction of 1,4-Dimethoxyphthalazines via a Bicyclization/Ring-Opening Mechanism

Synthesis ◽  
2020 ◽  
Author(s):  
Jeong Kyun Im ◽  
Ilju Jeong ◽  
Jun-Ho Choi ◽  
Won-jin Chung ◽  
ByeongDo Yang ◽  
...  
Keyword(s):  
Ring Opening ◽  
Reaction Conditions ◽  
Ring Contraction ◽  
Silyl Group ◽  
Favorskii Rearrangement ◽  
Mechanistic Analysis ◽  
Group A ◽  
Overall Efficiency ◽  
Trichloroisocyanuric Acid

AbstractAn unprecedented N-chlorinative ring contraction of 1,2-diazines was discovered and investigated with an electrophilic chlorinating reagent, trichloroisocyanuric acid (TCICA). Through optimization and mechanistic analysis, the assisting role of n-Bu4NCl as an exogenous nucleophile was identified, and the optimized reaction conditions were applied to a range of 1,4-dimethoxyphthalazine derivatives. Also, an improvement of overall efficiency was demonstrated by the use of a labile O-silyl group. A bicyclization/ring-opening mechanism, inspired by the Favorskii rearrangement, was proposed and supported by the DFT calculations. Furthermore, the efforts on scope expansion as well as the evaluation of other electrophilic promoters revealed that the newly developed ring contraction reactivity is a unique characteristic of 1,4-dimethoxyphthalazine scaffold and TCICA.

Synthesis of Optically Active Hydroxyalkyl Cycloheptatrienes: A Key Step in the Total Synthesis of 6,11-Methylene-LXB4

Synlett ◽  
2020 ◽  
Vol 32 (01) ◽  
pp. 45-50
Author(s):  
Udo Nubbemeyer ◽  
Analuisa Nava ◽  
Lukas Trippe ◽  
Andrea Frank ◽  
Lars Andernach ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Total Synthesis ◽  
Structure Elucidation ◽  
Butyl Ester ◽  
Optically Active ◽  
Chiral Hplc ◽  
Reaction Conditions ◽  
Acid Product ◽  
Tert Butyl ◽  
Nabh4 Reduction

AbstractStarting from methyl cycloheptatrienyl-1-carboxylate, 6-acylation was successfully achieved employing glutaryl chloride in the presence of AlCl3 under controlled reaction conditions to furnish keto carboxylic acid product. After protection of this keto carboxylic acid as tert-butyl ester, reagent-controlled enantioselective reductions delivered configuration-defined methyl-6-hydroxylalkyl cycloheptatriene-1-carboxylates with up to 80% ee. Whereas simple NaBH4 reduction of the keto carboxylic acid and subsequent lactonization afforded a methyl-6-tetrahydropyranonyl cycloheptatriene-1-carboxylate. Resolution using chiral HPLC delivered the product enantiomers with up to >99% ee Finally, ECD analyses enabled structure elucidation. The products are used as key intermediates in enantioselective 6,11-methylene-lipoxin B4 syntheses.

scholarly journals Utilizing a Facebook closed group for EFL e-learning environment: Students’ views

2021 ◽  
Vol 8 (3) ◽  
pp. 1026-1044
Author(s):  
Martha Nandari Santoso
Keyword(s):  
Learning Environment ◽  
Foreign Language ◽  
Online Classes ◽  
Online Class ◽  
Face To Face ◽  
Closed Group ◽  
E Learning ◽  
Group A ◽  
Display Quality

This study was conducted out of the researcher’s teaching reflection while teaching English as a foreign language (EFL) online class during the pandemic of COVID-19, a time when face-to-face courses had to be converted to online classes. Her choice of educational tool for her EFL e-learning environment utilized a Facebook closed group. Her experiences in utilizing a Facebook closed group for her EFL e-learning environment and the students’ views were the main topics of this study. Eighteen EFL freshmen participants were selected in this study. The researcher used data from a questionnaire with some closed and open-ended questions. The findings indicated that the students found the Facebook closed group a comfortable, practical, and useful e-learning environment. The students’ familiarity with the interface helped them to immediately focus on the class activities instead of learning how to use the tool. Most students viewed the Facebook closed group as positive for class interactions, creative work, opinions, and express feelings. A few dislike voices were related to the display quality of Facebook, the asynchronous and silent communication on Facebook. Accordingly, utilizing a Facebook closed group might be worth considering for learners who have not been adequately prepared with the technology for joining an online class. 

A practical chlorination of tert-butyl esters with PCl3 generating acid chlorides

2020 ◽  
Vol 44 (5-6) ◽  
pp. 301-304
Author(s):  
Xiaofang Wu ◽  
Lei Zhou ◽  
Ruoqi Yang ◽  
Fengzhe Guo ◽  
Zi-Long Tang ◽  
...  
Keyword(s):  
Aromatic Acid ◽  
Aliphatic Acid ◽  
Acid Chlorides ◽  
Alkyl Esters ◽  
Reaction Conditions ◽  
Simple Reaction ◽  
Tert Butyl ◽  
Butyl Esters ◽  
Plausible Mechanism ◽  
First Time

For the first time, using PCl3, a range of tert-butyl esters is chlorinated successfully, allowing access of both aromatic acid chlorides and aliphatic acid chlorides in good yields. The method features simple reaction conditions and wide substrate scope. Various tert-butyl esters including aryl esters, alkenyl esters, and alkyl esters were tolerated well in the reaction. A plausible mechanism is proposed.

scholarly journals Consumer-led experience customization: a socio-spatial approach

2018 ◽  
Vol 29 (2) ◽  
pp. 206-229 ◽  
Author(s):  
Edwin N. Torres ◽  
Peter Lugosi ◽  
Marissa Orlowski ◽  
Giulio Ronzoni
Keyword(s):  
Design Methodology ◽  
Participant Observation ◽  
Organizational Resources ◽  
Content Type ◽  
Face To Face ◽  
Virtual Spaces ◽  
Spatial Approach ◽  
Group A ◽  
Empirical Context ◽  
New Consumer

Purpose Adopting a socio-spatial approach, this study develops a consumer-centric conception of service experience customization. In contrast to existing service customization research, which has focused on company-centric approaches, the purpose of this paper is to examine the practices through which consumers use, abuse, subvert, transform, or complement organizational resources to construct their consumption experiences. Design/methodology/approach The empirical context for this study is a Meetup group: a consumer network organized around members’ shared interests and activities in theme parks. The research utilized participant observation of members’ face-to-face activities during two years and over 80 events, interviews with key informants, and content analysis of online interactions. Findings The findings outline how consumers interact across physical and virtual spaces utilizing technologies and material objects. The data are used to propose a new consumer-centric conceptualization of experience customization, distinguishing between three modes: collaborative co-production, cooperative co-creation, and subversive co-creation. Originality/value It is argued that the three modes of customization provide a way to understand how consumers mobilize and (re)deploy organizational resources to create experiences that may complement existing service propositions, but may also transform them in ways that challenge the service provider’s original goals and expectations. Furthermore, this study identifies the factors that shape which modes of customization are possible and how they are enacted. Specifically, the discussion examines how experiential complexity, governability, the compatibility of consumer and organizational practices, and the collective mobilization of resources may determine the scope and form of customization.

Structural Variations in Tetrasilver(I) Complexes of Pyrazolate-bridged Compartmental N-Heterocyclic Carbene Ligands

2009 ◽  
Vol 64 (11-12) ◽  
pp. 1542-s1554 ◽  
Author(s):  
Maria Georgiou ◽  
Simone Wöckel ◽  
Vera Konstanzer ◽  
Sebastian Dechert ◽  
Michael John ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Nmr Spectroscopy ◽  
Carbene Ligands ◽  
Structural Variations ◽  
X Ray ◽  
Face To Face ◽  
Tert Butyl ◽  
X Ray Crystallography

A set of pyrazole-bridged bis(imidazolium) compounds [H3L1]X2 - [H3 L4]X2 (L1 = 3,5-bis[1-(tert-butyl)imidazolium-1-ylmethyl]-1H-pyrazole; L2 = 3,5-bis[1-(tert-butyl)imidazolium- 1-ylmethyl]-4-phenyl-1H-pyrazole; L3 = 3,5-bis[1-(1-adamantyl)imidazolium-1-ylmethyl]-1Hpyrazole; L4 = 3,5-bis[1-(1-adamantyl)imidazolium-1-ylmethyl]-4-phenyl-1H-pyrazole; X = Cl−, BF4 − or PF6 −) has been prepared, and three compounds have been characterized by X-ray crystallography. The unique [H3L4][H2L4](PF6)3 features a dimeric face-to-face arrangement of two molecules due to the involvement of both the pyrazole-NH and the imidazolium C2H in hydrogen bonding. [H3L1]X2 - [H3L4]X2 serve as precursors for silver(I) complexes with compartmental pyrazolate-bridged bis(NHC) ligands. The complexes have been readily prepared by the Ag2O route and feature either the known [(L1−4)2Ag4]2+ or the new [(H2L1)4Ag4]8+ motif, depending on the solvent for the reaction (MeCN or acetone). [(H2L1)4Ag4](PF6)8 contains a central (pzAg)4 ring with pendant imidazolium side arms. Upon further reaction with Ag2O in MeCN it was found to undergo transformation to the corresponding [(L1)2Ag4](PF6)2. All complexes have been thoroughly studied by NMR spectroscopy in solution, and preliminary luminescence data of [(H2L1)4Ag4](PF6)8 have been recorded

Gas- and liquid-phase proton NMR study of the syn-anti conformer equilibrium of ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl and neopentyl nitrite

1986 ◽  
Vol 90 (18) ◽  
pp. 4353-4358 ◽  
Author(s):  
Claire B. Conboy ◽  
J. Paul Chauvel ◽  
Phillip O. Moreno ◽  
Nancy S. True ◽  
C. M. Ott
Keyword(s):  
Liquid Phase ◽  
Proton Nmr ◽  
Tert Butyl ◽  
Nmr Study ◽  
Anti Conformer
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