Solvolysis of crowded 2-adamantyl derivatives: comparison with the 2-norbornyl system

Faulkner, D.; McKervey, M. Anthony; Lenoir, Dieter; Senkler, C. A.; Schleyer, Paul von Ragué

doi:10.1016/s0040-4039(00)72439-7

Cited by 7 publications

(3 citation statements)

References 12 publications

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“…In 60% aqueous ethanol at 75°C, the relative rate of 11 is exceeded by that of 14 by a factor of 2.2, and 13 solvolyzes 63 times as fast as 11. 54 This reversal of the relative rates, comparing S N 2 reactions with QN 3 and solvolyses, is found not only in the case of 2-adamantyl and 4,4-dimethyl-2-adamantyl substrates, but also for similar cyclopentyl substrates ( Figure 1). It provides further proof that the formation of azides from sulfonates and QN 3 in nonpolar solvents should be described as an S N 2 reaction.…”

Section: With Steric Hindrancementioning

confidence: 84%

Hexadecyltributylphosphonium Azide - A Highly Potent Reagent for the Synthesis of Unusual Azides

Banert¹

2007

Synthesis

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Hexadecyltributylphosphonium azide (QN 3 ) is easily accessible and highly lipophilic, resulting in good solubility in nonpolar solvents like cyclohexane. The low melting point of this reagent allows convenient usage as a (supercooled) melt. Thus, extremely rapid nucleophilic substitution reactions and isolation of unstable products by simple re-condensation are possible. Utilizing these properties, the application of QN 3 in the synthesis of organic azides is successful even in cases in which classical methods have failed. This is demonstrated in this review by several examples, including unstable starting materials and substrates with steric hindrance or i-strain, or dealing with rapid subsequent reactions, either desired or not, of the generated azides.

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Section: With Steric Hindrancementioning

confidence: 84%

Hexadecyltributylphosphonium Azide - A Highly Potent Reagent for the Synthesis of Unusual Azides

Banert¹

2007

Synthesis

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“…The minor product (6%, longer retention time on a 5% Carbowax 1.5 m X 3 mm o.d. column) had the mass spectrum36 210 (M-+) (7), 192 (100), 160 (20), 133 (40), 93 (24), 91 (69), 79 (41), 59 (20), 45 (80), 41 (34). (b) From lh-OTres.…”

Section: Experimental Section33mentioning

confidence: 99%

“…while the ratio k^b/k^a is 275 times higher than kik/^u (at 75 °C). 24 In the 2-exo-norbornyl series, a 7,7-dimethyl substitution decreases ka.y[e¡k\\ by 102•6, while a 6,6-dimethyl substitution increases ka.Me/kn by 103•7 over the parent system.24•25 It is also noteworthy that ka.MS/kn for the mfo-protoadamantyl series (/¿2b/^2h) is slightly higher than the limiting value, although some participation in the solvolysis of the secondary substrate (2h) was deduced from other type of arguments.5c'8b This strengthens our view that the variations of the ka,Me/kh in these systems originate in steric interactions. Therefore, the ka.\/[e/kh ratio is not a reliable criterion for bridging in complex systems.26 Another possible argument for bridging in 4-exo-protoadamantyl substrates is the decrease50 in kexo/kcnáo ratio in going from secondary (k2g/k2b) to tertiary 4-protoadamantyl derivatives (k2a/k2b)• Again, logical analysis shows this is not an independent argument, but follows directly from the variations in ka.Me/kn for the two epimers (decreased for exo, increased for endo) discussed above.…”

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confidence: 99%