Nucleophilic substitution at phosphorus. The effect of ion association on the stereochemistry and rate of substitution at phosphorus in a six-membered ring phosphate

The synthesis of bis(triarylstannanethiocarbonyl)disulfides was attempted by oxidation of lithium triaryl stannane carbodithioates with molecular iodine. Unexpectedly, the desired compounds are highly unstable and undergo subsequent fragmentation giving triarylstannyl triarylstannanecarbodithioates. The proposed mechanism for this transformation assumes intramolecular nucleophilic substitution with formation of six-membered ring transition complex, stabilized by interaction between tin and thiocarbonyl sulfur atom. Obtained compounds were identified by mass-spectrometry and NMR spectroscopies, and their structures were analyzed by X-ray diffraction. These molecules show the existence of intramolecular non-bonding interactions between the sulfur atoms of the thiocarbonyl moieties and tin atoms. These interactions reflect the tin - sulfur affinity and are the main driving force in the fragmen tation of bis(triphenylstannanethiocarbonyl)disulfides.

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N,N-Dialkyl-N′-Chlorosulfonyl Chloroformamidines in Heterocyclic Synthesis. Part XV. Some Unexpected Reactions with Anilines

Australian Journal of Chemistry ◽

10.1071/ch18252 ◽

2018 ◽

Vol 71 (8) ◽

pp. 610

Author(s):

Dylan Innes ◽

Michael V. Perkins ◽

Andris J. Liepa ◽

Craig L. Francis

Keyword(s):

Nucleophilic Substitution ◽

Membered Ring ◽

Heterocyclic Synthesis ◽

Screening Programs ◽

Bioactive Molecule ◽

Sterically Hindered

N,N-Dimethyl-N′-chlorosulfonyl chloroformamidine 1a underwent reactions with various anilines. In addition to the benzo[e][1,2,4]thiadiazine dioxides 8, from 1,3-NCC bis-nucleophilic substitution and bis-anilino adducts 9, some unexpected products were formed, particularly when sterically hindered or electron-poor anilines were used. In these cases, products such as the [1,3,2,4,6]dithiatriazine 1,1,3,3-tetraoxides 17 and, on occasion, N,N,5-trimethyl-4-(arylimino)-4,5-dihydro-[1,3,5]triazin-2-amines 14 were produced in significant yields. Reaction of dichloride 1a with 3-bromoaniline afforded the unusual eight-membered-ring product 2,6-bis(3-bromophenyl)-3,7-bis(dimethylamino)-2H,6H-[1,5,2,4,6,8]dithiatetrazocine 1,1,5,5-tetraoxide 28, in addition to the dithiatriazine tetraoxide 17k. These uncommon heterocyclic structures are of interest for bioactive molecule discovery screening programs.

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ChemInform Abstract: Nucleophilic Substitution of the Carbon Hydrogen on the Five-Membered Ring of Indoles

ChemInform ◽

10.1002/chin.200018276 ◽

2010 ◽

Vol 31 (18) ◽

pp. no-no

Author(s):

John A. Joule

Keyword(s):

Nucleophilic Substitution ◽

Membered Ring

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Purine analogues. I. The status of Hückel molecular orbital calculations as predictors of proton shifts, basic strengths, and reactivity

Canadian Journal of Chemistry ◽

10.1139/v69-183 ◽

1969 ◽

Vol 47 (7) ◽

pp. 1129-1138 ◽

Cited By ~ 18

Author(s):

Brian M. Lynch ◽

Allan J. Robertson ◽

John G. K. Webb

Keyword(s):

Nucleophilic Substitution ◽

Molecular Orbital ◽

Chemical Shifts ◽

Ionic Species ◽

Membered Ring ◽

Molecular Orbital Calculations ◽

Electron Densities ◽

Purine Analogues ◽

The Status ◽

Proton Chemical Shifts

A detailed series of molecular orbital calculations based on the HMO method has been made for the various possible ionic species of purine, pyrazolo(3,4-d)pyrimidine, v-triazolo(4,5-d)pyrimidine, and pyrazolo(3,4-b)pyridine. π-Electron densities and localization and delocalization energies for nucleophilic substitution have been derived.The results are compared with the observed proton chemical shifts in the conjugate acids of these molecules, with the relative rates of nucleophilic piperidinodehalogenations in the neutral molecules, and with the ionization constants.It is concluded that it is possible to reconcile the calculations with experimental results for the various positions within a six-membered ring, but that positions in six- and five-membered rings cannot be directly compared. The electron densities seem to be of little value in correlating the observed ionization patterns of purines and their analogues.

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