Azide and Cyanide Displacements via Hypervalent Silicate Intermediates

Soli, Eric D.; Manoso, Amy S.; Patterson, Margaret F.; DeShong, Philip; Favor, David A.; Hirschmann, Ralph; Smith, Amos B.

doi:10.1021/jo982302d

Cited by 146 publications

(89 citation statements)

References 53 publications

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“…[30] Their conclusion that the reactions with NaCN and AgCN follow the same mechanism and that "the observed regioselectivity with both metal cyanides (…) cannot be explained as variations in the hardness of the electrophilic carbon induced by the interactions between the metal cation and the halogen" found little attention. [31] In agreement with "older hypotheses", the formation of isonitriles with AgCN (Scheme 6) was explained by the "participation of a species (non-free CN À ) in which the Ag + ion is bonded to the carbon atom." [30] The formation of 1-isocyanoadamantane from 1-chloroadamantane and trimethylsilyl cyanide in the presence of TiCl 4 (Scheme 7) demonstrates that blocking of the carbon atom of cyanide is not restricted to Ag + .…”

Section: Calculated Barriers For Identity Reactions Of Ambident Nuclesupporting

confidence: 65%

Farewell to the HSAB Treatment of Ambident Reactivity

Mayr¹,

Breugst²,

Ofial³

2011

Angew Chem Int Ed

258

211

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The concept of hard and soft acids and bases (HSAB) proved to be useful for rationalizing stability constants of metal complexes. Its application to organic reactions, particularly ambident reactivity, has led to exotic blossoms. By attempting to rationalize all the observed regioselectivities by favorable soft-soft and hard-hard as well as unfavorable hard-soft interactions, older treatments of ambident reactivity, which correctly differentiated between thermodynamic and kinetic control as well as between different coordination states of ionic substrates, have been replaced. By ignoring conflicting experimental results and even referring to untraceable experimental data, the HSAB treatment of ambident reactivity has gained undeserved popularity. In this Review we demonstrate that the HSAB as well as the related Klopman-Salem model do not even correctly predict the behavior of the prototypes of ambident nucleophiles and, therefore, are rather misleading instead of useful guides. An alternative treatment of ambident reactivity based on Marcus theory will be presented.

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Section: Calculated Barriers For Identity Reactions Of Ambident Nuclesupporting

confidence: 65%

Farewell to the HSAB Treatment of Ambident Reactivity

Mayr¹,

Breugst²,

Ofial³

2011

Angew Chem Int Ed

258

211

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“…[14] b-d-Glucopyranosyl azide (3) was prepared according to Soli et al [15] or Ogawa et al [16] The 1 H and 13 C NMR data for compounds 1-3 were consistent with the structures (see the literature, [14,16] respectively). a-d-Mannopyranosyl azide (4): 1,2,3,4,6-Penta-O-acetyld-mannose (4a) was prepared according to Watt and Williams.…”

Section: Synthesis Of Substratesmentioning

confidence: 78%

Glycosyl Azides – An Alternative Way to Disaccharides

et al. 2007

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This paper is dedicated to the memory of Prof. Zoltµn Gyçrgydeàk, who greatly contributed to the chemistry of glycosyl azides.Abstract: Glycosyl azides are shown to be efficient donors for b-galactosidases, b-glucosidases and amannosidases. Only a-galactosidases do not cleave the respective glycosyl azide 1 and, moreover, they exhibit competitive inhibition (especially a-galactosidase from Talaromyces flavus). High water solubility and ready synthesis of glycosyl azides enable transglycosylation reactions even with difficult acceptors like N-acetyl-d-mannosamine in good yields. The versatility of glycosyl azides was demonstrated in the synthesis of five disaccharides -two of them are described for the first time. All the reactions were highly regioselective, yielding bA C H T U N G T R E N N U N G (1!6) isomers. bGalactosidase from E. coli proved to have the best synthetic capabilities. The present study shows that glycosyl azides are a valuable alternative to common p-nitrophenyl glycoside donors and in many synthetic reactions.

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“…The anomeric glycosyl azides were prepared from their respective peracetylated counterparts by reaction with HBr in AcOH under microwave irradiation. [21] The resulting glycosyl bromides were treated with trimethylsilyl azide and tetrabutylammonium fluoride, [22] again using microwave irradiation, which gave the desired peracetylated β-azido sugars for the [3 + 2] cycloaddition reactions in high yields (Ն 78 %). The procedure can be conveniently carried out on a gram scale.…”

Section: Resultsmentioning

confidence: 99%