The 9-decalyl and related cations. IV. Generation of cis- and trans-2-t-Butyl-9-decalyl cations through σ-routes by acetolysis

1978 ◽  
Vol 31 (4) ◽  
pp. 835 ◽  
Author(s):  
GE Gream ◽  
MH Laffer ◽  
AK Serelis
Keyword(s):  
Ion Pairs ◽  
Ring Expansion ◽  
Ion Pair ◽  
Membered Ring ◽  
Boat Conformation ◽  
Proton Abstraction ◽  
Conformational Interconversion ◽  
Anchimeric Assistance ◽  
Cis And Trans

The synthesis and solvolytic behaviour (in buffered acetic acid) of cis- and trans-9-t-butylspiro[4,5]-dec-6-yl p-toluenesulfonate (5) and (6) are described. The two compounds solvolyse with anchimeric assistance and undergo ring expansion with complete stereospecificity; the cis- and trans-esters yield trans- and cis-2-t-butyl-9-decalyl cation (8) and (7), respectively. To account for the stereospecificity, it is proposed that (6) must solvolyse through a boat conformation of the six-membered ring. Ring contraction (c. 8%), with the formation of the 1-(3'-t-butylcyclopentyl)cyclopentyl cation (presumably trans (36)), also takes place in the acetolysis of (6). ��� The possible role of ion-pairs in the reactions of (5) and (6) is examined. It is concluded that the anion in an ion-pair might be involved in olefin formation only when it (the anion) is ideally located for proton abstraction in the initially formed ion-pair (or that formed by conformational interconversion of the cationic moiety).

Octahedral cobalt(III) complexes in dipolar aprotic solvents. II. Association between cis- and trans-dichlorobisethylenediamine cobalt(III) cations,[Co en2 Cl2]+, and chloride and bromide ions in the solvents NN-dimethylformamide, dimethyl sulphoxide, and LVN-dimethylacetamide

1966 ◽  
Vol 19 (1) ◽  
pp. 43 ◽  
Author(s):  
WA Millen ◽  
DW Watts
Keyword(s):  
Spectrophotometric Method ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Dimethyl Sulphoxide ◽  
Aprotic Solvents ◽  
Ion Association Constants ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

Ion association constants at 30� have been determined for the cis-[Co en, Cl2]+Cl- ion pair in NN-dimethylformamide (DMF), NN-dimethylacetamide (DMA), and at 20.0�, 25.0�, and 30.0� in dimethyl sulphoxide (DMSO), by a spectrophotometric method. Association constants for the cis-[Co en2 Cl2]+Br- and the trans- [Co en2 Cl2]+Cl- ion pairs have also been determined in DMF at 30�.

The 9-decalyl and related cations. III. Generation of the 8-hydrindyl cation by solvolysis

1974 ◽  
Vol 27 (8) ◽  
pp. 1711 ◽  
Author(s):  
GE Gream ◽  
AK Serelis ◽  
TI Stoneman
Keyword(s):  
Ion Pairs ◽  
Cationic Species ◽  
Direct Route ◽  
Counter Ion ◽  
Product Composition ◽  
Cis And Trans

Acetolysis of 4-(cyclopent-1'-enyl)butyl and 3-(2'-methylenecyclopentyl)propyl derivatives, but not 3-(cyclohex-1'-enyl)propyl and 2-(2'-methylenecyclohexyl)ethyl derivatives, occurs with π-bond participation (95 and 92%, respectively) to give similar, including maybe identical, cationic species involving the 8-hydrindyl cation. On the basis of product composition, the 8-hydrindyl cations when generated from spiro[4,4]non-1-yl (σ-route) and cis- and trans-8-hydrindyl derivatives (direct route) are each different and are in turn different to those generated by the above π-routes. Reasons for the differences are discussed and the possible role of the counter-ion in ion-pairs is examined.

On the Concerted Ring Opening of Protonated Squalene Oxide and A-Ring Formation in the Biosynthesis of Lanosterol

2003 ◽  
Vol 68 (1) ◽  
pp. 202-210 ◽  
Author(s):  
B. Andes Hess
Keyword(s):  
Ring Opening ◽  
Density Functional ◽  
Reaction Pathway ◽  
Ring Expansion ◽  
Membered Ring ◽  
Ring Formation ◽  
Ring Closure ◽  
Primary Role ◽  
Transition Structure

Density functional calculations were performed on a model system of squalene oxide to study the mechanism of the formation of ring A in the biosynthesis of lanosterol from squalene. When (2Z)-6,7-epoxy-3,7-dimethyloct-2-ene was protonated, it was calculated to undergo a very facile ring opening of the oxirane in concert with the formation of the six-membered ring of the 4-(hydroxymethyl)-1,2,3,3-tetramethy1cyclohexyl cation. A study of the reaction pathway (IRC) indicates a very early transition structure in which the carbon- carbon double bond participates anchimerically in the ring-opening of the protonated oxirane. It is suggested that the primary role of the enzyme in this first step of the biosynthesis of lanosterol is protonation of the oxirane ring along with holding the substrate in the proper conformation for the concerted ring-closure to occur. The similarity between this mechanism and that recently proposed for concerted C-ring expansion and D-ring formation in the biosynthesis of lanosterol is discussed.

Stereospecific 1,3-H Transfer of Indenols Proceeds via Persistent Ion-Pairs Anchored By NH···Pi Interactions

2018 ◽  
Author(s):  
David Ascough ◽  
Fernanda Duarte ◽  
Robert Paton
Keyword(s):  
Computational Analysis ◽  
Ion Pairs ◽  
Ion Pair ◽  
Hydrogen Atom Transfer ◽  
Polar Solvents ◽  
Chirality Transfer ◽  
Activation Barriers ◽  
Sense And Avoid ◽  
Phase Dynamics ◽  
Pi Interactions

The base-catalyzed rearrangement of arylindenols is a rare example of a suprafacial [1,3]-hydrogen atom transfer. The mechanism has been proposed to proceed via sequential [1,5]-sigmatropic shifts, which occur in a selective sense and avoid an achiral intermediate. A computational analysis using quantum chemistry casts serious doubt on these suggestions: these pathways have enormous activation barriers and in constrast to what is observed experimentally, they overwhelmingly favor a racemic product. Instead we propose that a suprafacial [1,3]-prototopic shift occurs in a two-step deprotonation/reprotonation sequence. This mechanism is favored by 15 kcal mol<sup>-1</sup> over that previously proposed. Most importantly, this is also consistent with stereospecificity since reprotonation occurs rapidly on the same p-face. We have used explicitly-solvated molecular dynamics studies to study the persistence and condensed-phase dynamics of the intermediate ion-pair formed in this reaction. Chirality transfer is the result of a particularly resilient contact ion-pair, held together by electrostatic attraction and a critical NH···p interaction which ensures that this species has an appreciable lifetime even in polar solvents such as DMSO and MeOH.

The Crystal and Molecular Structure of sym-fac-(1,4,7-Triazaheptane)-(S)-aspartatocobalt(III) Diperchlorate Dihydrate

1994 ◽  
Vol 59 (5) ◽  
pp. 1052-1058 ◽  
Author(s):  
Jan Ondráček ◽  
Jana Ondráčková ◽  
Jaroslav Maixner ◽  
František Jursík
Keyword(s):  
Molecular Structure ◽  
Aspartic Acid ◽  
Crystal And Molecular Structure ◽  
Heavy Atom ◽  
Membered Ring ◽  
Boat Conformation ◽  
Hydrogen Atoms ◽  
Orthorhombic System ◽  
Anisotropic Temperature ◽  
Heavy Atom Method

The crystal and molecular structure of s-fac-[Co((S)-Asp)(dien)]ClO4 . HClO4 .2 H2O (dien = 1,4,7-triazaheptane) was solved by the heavy atom method. The position parameters of the non-hydrogen atoms and their anisotropic temperature parameters were refined based on 1 726 observed reflections with a final value of R = 0.073. The substance crystallizes in the orthorhombic system in the space group P212121, Z = 4, a = 8.506(1), b = 17.171(2), c = 13.277(1) Å. The structure involves hydrogen bonds between the O2, O4 and HN2 atoms of aspartic acid and the two molecules of water. The five-membered dien chelate rings take the asymmetric envelope conformations. The five-membered ring of (S)-aspartic acid possesses the symmetric envelope conformation whereas the six-membered ring exhibits the skew boat conformation.

scholarly journals Tripodal, Squaramide-Based Ion Pair Receptor for Effective Extraction of Sulfate Salt

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2751
Author(s):  
Damian Jagleniec ◽  
Marcin Wilczek ◽  
Jan Romański
Keyword(s):  
Ion Pairs ◽  
Binding Mode ◽  
Selective Extraction ◽  
Ion Pair ◽  
Hofmeister Series ◽  
Sulfate Salt ◽  
Lower Affinity ◽  
High Affinity ◽  
Binding Domains ◽  
Hydrated Sulfate

Combining three features—the high affinity of squaramides toward anions, cooperation in ion pair binding and preorganization of the binding domains in the tripodal platform—led to the effective receptor 2. The lack of at least one of these key elements in the structures of reference receptors 3 and 4 caused a lower affinity towards ion pairs. Receptor 2 was found to form an intramolecular network in wet chloroform, which changed into inorganic–organic associates after contact with ions and allowed salts to be extracted from an aqueous to an organic phase. The disparity in the binding mode of 2 with sulfates and with other monovalent anions led to the selective extraction of extremely hydrated sulfate anions in the presence of more lipophilic salts, thus overcoming the Hofmeister series.

ChemInform Abstract: THE ROLE OF SOLVENT IN CONJUGATE ADDITIONS LEADING TO CIS- AND TRANS-1-ALKYL-2-ARYL-3-CARBO(AROYL)AZIRIDINES

1977 ◽  
Vol 8 (40) ◽  
pp. no-no
Author(s):  
P. TARBURTON ◽  
P. B. WOLLER ◽  
R. C. BADGER ◽  
E. DOOMES ◽  
N. H. CROMWELL
Keyword(s):  
Conjugate Additions ◽  
Cis And Trans ◽  
Role Of Solvent

Ion pair binding by an l-tyrosine-based polymerizable molecular receptor

2015 ◽  
Vol 39 (8) ◽  
pp. 6216-6222 ◽  
Author(s):  
Szymon Zdanowski ◽  
Jan Romański
Keyword(s):  
Ion Pairs ◽  
Functional Polymers ◽  
Ion Pair

A polymerizable molecular receptor able to bind ion pairs and new functional polymers containing the receptor units were synthesized and characterized.

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