WordNet

arrange into a group or groups; "Can you group these shapes together?"
(chemistry) two or more atoms bound together as a single unit and forming part of a molecule (同)radical, chemical group
any number of entities (members) considered as a unit (同)grouping
a set that is closed, associative, has an identity element and every element has an inverse (同)mathematical group
form a group or group together (同)aggroup
the activity of putting things together in groups
a system for classifying things into groups (同)pigeonholing
the condition of sharing in common with others (as fellows or partners etc.) (同)involvement
arranged into groups (同)sorted

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(…の)『群れ』,集まり,小集団《+of+名》 / (主義・系統・種類などを同じくする人・物の)『派』,『団体』 / (ポミュラーソング歌手の)グループ / (動・植物分類上の)群;(化学の)基,原子団;(地質学上の)界;(数学の)群;(言語学上の)語派 / …‘を'一群に集める,一団にする《+『名』+『together』》 / (系統的に)…‘を'分類する,調和よく配合する《+『名』+『together』》 / 集まる,群(集団)をなす
グループに分けること;分類法 / (集まった物の)配置,配合
(…への)参加,加入《+『in』+『名』》

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/06/05 10:15:30」(JST)

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Neighbouring group participation (NGP) (also known as anchimeric assistance) in organic chemistry has been defined by IUPAC as the interaction of a reaction centre with a lone pair of electrons in an atom or the electrons present in a sigma bond or pi bond ^[1]. When NGP is in operation it is normal for the reaction rate to be increased. It is also possible for the stereochemistry of the reaction to be abnormal (or unexpected) when compared with a normal reaction. While it is possible for neighbouring groups to influence many reactions in organic chemistry (e.g. the reaction of a diene such as 1,3-cyclohexadiene with maleic anhydride normally gives the endo isomer because of a secondary effect {overlap of the carbonyl group π orbitals with the transition state in the Diels-Alder reaction}) this page is limited to neighbouring group effects seen with carbocations and S_N2 reactions.

NGP by heteroatom lone pairs

A classic example of NGP is the reaction of a sulfur or nitrogen mustard with a nucleophile, the rate of reaction is much higher for the sulfur mustard and a nucleophile than it would be for a primary alkyl chloride without a heteroatom.

In sugar chemistry anchimeric assistance is an example of NGP.

NGP by an alkene

The π orbitals of an alkene can stabilize a transition state by helping to delocalize the positive charge of the carbocation. For instance the unsaturated tosylate will react more quickly (10¹¹ times faster for aqueous solvolysis) with a nucleophile than the saturated tosylate.

The carbocationic intermediate will be stabilized by resonance where the positive charge is spread over several atoms, in the diagram below this is shown.

Here is a different view of the same intermediates.

Even if the alkene is more remote from the reacting center the alkene can still act in this way. For instance in the following alkyl benzenesulfonate the alkene is able to delocalise the carbocation.

Also the increase in the rate of the S_N2 reaction of allyl bromide with a nucleophile compared with the reaction of n-propyl bromide is because the orbitals of the π bond overlap with those of the transition state. In the allyl system the alkene orbitals overlap with the orbitals of a S_N2 transition state.

NGP by a cyclopropane, cyclobutane or a homoallyl group

If Cyclopropylmethyl chloride is reacted with ethanol and water then a mixture of 48% cyclopropylmethyl alcohol, 47% cyclobutanol and 5% homoallyl alcohol (but-3-enol) is obtained. This is because the carbocationic intermediate is delocalised onto many different carbons through a reversible ring opening.

NGP by an aromatic ring

In the case of a benzyl halide the reactivity is higher because the S_N2 transition state enjoys a similar overlap effect to that in the allyl system.

An aromatic ring can assist in the formation of a carbocationic intermediate called a phenonium ion by delocalising the positive charge.

When the following tosylate reacts with acetic acid in solvolysis then rather than a simple S_N2 reaction forming B, a 48:48:4 mixture of A, B and (C+D) was obtained ^[2] ^[3].

The mechanism which forms A and B is shown below.

External links

A PhD thesis written on this subject is at here.
IUPAC definition

References

^ Advanced organic chemistry, page 314, Jerry March (4th Ed), Wiley-Interscience.
^ Studies in Stereochemistry. I. The Stereospecific Wagner-Meerwein Rearrangement of the Isomers of 3-Phenyl-2-butanol Donald J. Cram J. Am. Chem. Soc.; 1949; 71(12); 3863-3870. Abstract
^ Studies in Stereochemistry. V. Phenonium Sulfonate Ion-pairs as Intermediates in the Intramolecular Rearrangements and Solvolysis Reactions that Occur in the 3-Phenyl-2-butanol System Donald J. Cram J. Am. Chem. Soc.; 1952; 74(9); 2129-2137 Abstract.

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English Journal

Electrospray ionization tandem mass spectrometry study of six isomeric cationic amphiphiles with ester/amide linker.

Vijay Darshan D1, Chandar BG, Srujan M, Chaudhuri A, Prabhakar S.Author information 1National Centre for Mass Spectrometry, CSIR-Indian Institute of Chemical Technology, Hyderabad, 500007, India.AbstractRATIONALE: Isomeric cationic amphiphiles differing only in the orientation of the linker group have been demonstrated to possess dramatically changed gene transfer efficacies. Studies aimed at understanding structure-stability correlations of such isomeric cationic amphiphiles at the molecular level are yet to be undertaken. Such studies may throw significant new insights into the mechanistic origin on their contrasting bioactivities.
Rapid communications in mass spectrometry : RCM.Rapid Commun Mass Spectrom.2014 Jun 15;28(11):1209-14. doi: 10.1002/rcm.6892.
RATIONALE: Isomeric cationic amphiphiles differing only in the orientation of the linker group have been demonstrated to possess dramatically changed gene transfer efficacies. Studies aimed at understanding structure-stability correlations of such isomeric cationic amphiphiles at the molecular level
PMID 24760561

Stereochemistry of intramolecular cyclization of tetra-β-(1→6)-D-glucosamines and related tetrasaccharides: the role of the conformational stereocontrol and the neighboring group participation.

Titov DV1, Gening ML, Gerbst AG, Chizhov AO, Tsvetkov YE, Nifantiev NE.Author information 1Laboratory of Glycoconjugate Chemistry, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, 119991 Moscow, Russia.AbstractThe effect of reaction conditions, the nature of a leaving group, and a substituent at C-2 in the glycosylating monosaccharide on the stereochemical outcome of cyclization of linear tetra-β-(1→6)-d-glucosamines and some 'mixed' tetrasaccharides comprising glucose and glucosamine residues has been examined. Toluene and nitrile solvents improved the β-stereoselectivity of cyclization, however, the overall efficiency of the formation of cyclic products in these solvents was lower than that in dichloromethane. The use of bromide or pentenyl glycoside as leaving groups instead of the thioglycoside did not increase the β-stereoselectivity. Replacement of the N-phthaloyl group in the glycosylating unit by N-Troc one did not affect the stereoselectivity of cyclization, while the tetrasaccharides, which contained 2-O-benzoyl glucose instead of glucosamine as the glycosyl donor moiety, were found to provide β-linked cyclic products exclusively. Using this finding, two cyclic tetrasaccharides with alternate or adjacent arrangement of two glucose and two glucosamine units have been efficiently synthesized. These cycles were intended for the preparation of divalent glycoclusters with different ligand orientation. The difference in the stereoselectivity of cyclization of glucose and glucosamine precursors was accounted for by more effective anchimeric participation of the O-benzoyl group as compared to N-Phth and N-Troc counterparts that was confirmed by calculations of the stabilization energy and rotational barriers around C2-O/N bond in the corresponding glycosyl cations. Only the 2-O-benzoylated glycosyl cation proved to be able to form a stabilized dioxalenium intermediate, which provides stereospecific β-glycosylation.
Carbohydrate research.Carbohydr Res.2013 Nov 15;381:161-78. doi: 10.1016/j.carres.2012.12.005. Epub 2012 Dec 20.
The effect of reaction conditions, the nature of a leaving group, and a substituent at C-2 in the glycosylating monosaccharide on the stereochemical outcome of cyclization of linear tetra-β-(1→6)-d-glucosamines and some 'mixed' tetrasaccharides comprising glucose and glucosamine residues has been
PMID 23312144

Structure determination and total synthesis of (+)-16-hydroxy-16,22-dihydroapparicine.

Hirose T1, Noguchi Y, Furuya Y, Ishiyama A, Iwatsuki M, Otoguro K, Omura S, Sunazuka T.Author information 1Kitasato Institute for Life Sciences and Graduate School of Infection Control Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.AbstractHerein, we describe the first asymmetric total synthesis and determination of the relative and absolute stereochemistry of naturally occurring 16-hydroxy-16,22-dihydroapparicine. The key steps include 1) a novel phosphinimine-mediated cascade reaction to construct the unique 1-azabicyclo[4.2.2]decane core, including a pseudo-aminal-type moiety; 2) a highly stereospecific 1,2-addition of 2-acylindole or a methylketone through a Felkin-Anh transition state for the construction of a tetrasubstituted carbon center; and 3) an intramolecular chirality-transferring Michael reaction of the ketoester, with neighboring-group participation, to introduce a chiral center at C15 in the target molecule. In addition, we evaluated the antimalarial activity of synthetic (+)-(15S,16R)-16-hydroxy-16,22-dihydroapparicine and its intermediate against chloroquine-resistant Plasmodium falciparum (K1 strain) parasites.
Chemistry (Weinheim an der Bergstrasse, Germany).Chemistry.2013 Aug 5;19(32):10741-50. doi: 10.1002/chem.201300292. Epub 2013 Jun 20.
Herein, we describe the first asymmetric total synthesis and determination of the relative and absolute stereochemistry of naturally occurring 16-hydroxy-16,22-dihydroapparicine. The key steps include 1) a novel phosphinimine-mediated cascade reaction to construct the unique 1-azabicyclo[4.2.2]dec
PMID 23788004

Japanese Journal

グリコシル化反応の計算化学

Satoh Hiroko,Nukada Tomoo
Trends in glycoscience and glycotechnology 26(147-149), 11-27, 2014-01
NAID 40020181996

グリコシル化反応の計算化学

Satoh Hiroko,Nukada Tomoo
Trends in Glycoscience and Glycotechnology 26(147), 11-27, 2014
グリコシル化反応は、グリコシド結合を形成し糖鎖を生成する化学反応であり、グライコサイエンスにおける重要な化学反応の1つである。この糖鎖合成における鍵反応のメカニズムを理解することは、生体内におけるグリコシル化反応についての洞察を深めるだけでなく、合理的な戦略に基づいた化学合成技術の発展にも貢献すると期待される。本稿では、グリコシル化の反応機構に関する研究について、計算化学的アプローチによる取組みに …
NAID 130004841381

アキシアル・リッチな糖供与体を用いたO-グリコシル化反応

Yamada Hidetoshi
Trends in glycoscience and glycotechnology 23(129), 122-133, 2011-05-31
ピラノース環の立体配座を、アキシアル配向した置換基がより多い立体配座に固定して行ったL-O-ラムノシル化反応とD-O-グルコシル化反応について述べる。本稿では、このような立体配座をアキシアル・リッチな立体配座と呼ぶ。どちらの糖も、隣接したトランスジオールに嵩高いシリル基を導入すると、そのピラノース環をアキシアル・リッチな立体配座に固定できた。このように立体配座を束縛したL-ラムノース誘導体は、トリ …
NAID 10029582877