Some lewis acid catalysed reactions of 2,2,2-trichloroethyl 6-diazopenicillanate

GIDDINGS, P. J.; John, D. I.; Thomas, Eric J.

doi:10.1016/s0040-4039(01)85434-4

Cited by 20 publications

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“…In Thomas's case, the corresponding S-ester was isolated in low yield. [7] Since thiocarboxylic acids may exist as a tautomeric mixture of thiol and thione forms, [8] it is interesting to investigate the chemoselectivity of this reaction. Here we report our study on the reaction of thioacetic S-acid with α-diazo carbonyl compounds, catalyzed by an Rh II catalyst and a Lewis acid.…”

Section: Introductionmentioning

confidence: 99%

Study of the Rh₂(OAc)₄‐ or BF₃·OEt₂‐Mediated Reaction of Thioacetic S‐Acid with α‐Diazocarbonyl Compounds

et al. 2003

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Section: Introductionmentioning

confidence: 99%

Study of the Rh₂(OAc)₄‐ or BF₃·OEt₂‐Mediated Reaction of Thioacetic S‐Acid with α‐Diazocarbonyl Compounds

et al. 2003

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“…Alkylations of sterically demanding alcohols [54][55][56][57][58]. The scope of the Williamson ether synthesis, in which the alcohol is first converted stoichiometrically into an alcoholate which is then alkylated with an alkyl halide, is significantly broader.…”

Section: Alkylation Of Alcoholsmentioning

confidence: 99%

The Alkylation of Heteroatoms

Dörwald

2004

Side Reactions in Organic Synthesis

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Although carbon-heteroatom bonds are often easier to make than C-C bonds, and are therefore often chosen as retrosynthetic points of disconnection, some non-carbon nucleophiles can be difficult to alkylate. Problems can arise when the nucleophile is highly basic and hard, for these will preferentially attack (hard) protons and cause elimination instead of being alkylated [1]. Similarly, sterically demanding nucleophiles will also tend to attack protons faster than undergo alkylation. Ambident nucleophiles, such as amides, phenols, thiocyanate, or nitrite, can be a further cause of problems, because a variety of different products can be formed, depending on the type of electrophile chosen and on the precise reaction conditions [2]. Substrates with two or more similar nucleophilic groups, for example aminophenols or hydroxybenzoic acids, can often be alkylated with high chemoselectivity, but the outcome of these reactions can be difficult to predict. In the following sections the alkylation of the most common, trouble-causing non-carbon nucleophiles will be discussed.As for carbanions, the reactivity of anionic non-carbon nucleophiles depends on the cation. The nucleophilicity and basicity of a given anionic nucleophile will usually be enhanced if it does not form strong bonds either with the cation or with the solvent. Hard cations, for example Li + or Ti 4+ , will significantly reduce the reactivity of hard anions (RO -, R 2 N -, F -), whereas soft cations (Cs + , Cu + , Pd 2+ ) will form strong bonds with soft anions (RS -, I -, CN -, H -, R -) and thereby reduce their reactivity. 6.1 Alkylation of FluorideHydrogen fluoride (pK a 3.2 in water) is the hydrogen halide with the lowest acidity, and fluoride is, therefore, a rather strong base. Nucleophilic substitutions with fluoride do not usually proceed smoothly, despite the strength of the C-F bond, and alkenes are often obtained instead of alkyl fluorides if simple alkyl monohalides are treated with fluoride under basic reaction conditions. Eliminations occur particularly readily from alkyl fluorides with an electron-withdrawing group in the b position. Common reagents for displacing halides or related leaving groups by fluoride include AgF, KF, CsF, Bu 4 NF [3], HF, and SbF 5 , and suitable solvents are ethylene6 230 Scheme 6.1. Displacement of different leaving groups by fluoride [5-8].6.2 Alkylation of Aliphatic Amines groups is because of negative hyperconjugation between the (antibonding) r* C-F orbitals and the lone pairs on fluorine (see Section 3.4). Alkylation of Aliphatic AminesThe most conspicuous property of aliphatic amines, apart from their fishy smell, is their high basicity, which usually precludes N-alkylations under acidic reaction conditions (last reaction, Scheme 6.3). Hence, alkylation of amines with tertiary alkyl groups is not usually possible without the use of highly stabilized carbocations which can be formed under basic reaction conditions. Rare exceptions are N-alkylations of amines via radicals (Scheme 4.2), copper-catalyzed propar...

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ChemInform Abstract: SOME LEWIS ACID CATALYZED REACTIONS OF 2,2,2‐TRICHLOROETHYL 6‐DIAZOPENICILLANATE

GIDDINGS¹,

John²,

Thomas³

1978

Chemischer Informationsdienst

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Some lewis acid catalysed reactions of 2,2,2-trichloroethyl 6-diazopenicillanate

Cited by 20 publications

References 5 publications

Study of the Rh₂(OAc)₄‐ or BF₃·OEt₂‐Mediated Reaction of Thioacetic S‐Acid with α‐Diazocarbonyl Compounds

Study of the Rh₂(OAc)₄‐ or BF₃·OEt₂‐Mediated Reaction of Thioacetic S‐Acid with α‐Diazocarbonyl Compounds

The Alkylation of Heteroatoms

ChemInform Abstract: SOME LEWIS ACID CATALYZED REACTIONS OF 2,2,2‐TRICHLOROETHYL 6‐DIAZOPENICILLANATE

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Some lewis acid catalysed reactions of 2,2,2-trichloroethyl 6-diazopenicillanate

Cited by 20 publications

References 5 publications

Study of the Rh2(OAc)4‐ or BF3·OEt2‐Mediated Reaction of Thioacetic S‐Acid with α‐Diazocarbonyl Compounds

Study of the Rh2(OAc)4‐ or BF3·OEt2‐Mediated Reaction of Thioacetic S‐Acid with α‐Diazocarbonyl Compounds

The Alkylation of Heteroatoms

ChemInform Abstract: SOME LEWIS ACID CATALYZED REACTIONS OF 2,2,2‐TRICHLOROETHYL 6‐DIAZOPENICILLANATE

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Study of the Rh₂(OAc)₄‐ or BF₃·OEt₂‐Mediated Reaction of Thioacetic S‐Acid with α‐Diazocarbonyl Compounds

Study of the Rh₂(OAc)₄‐ or BF₃·OEt₂‐Mediated Reaction of Thioacetic S‐Acid with α‐Diazocarbonyl Compounds