Detection, determination, and characterisation of amines

Zabicky, Jacob

doi:10.1002/9780470771082.ch3

Cited by 6 publications

(2 citation statements)

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“…Each of these organometallic complexes could modify the physiological environment of autotrophs in ways suggested by Saunders (1957) and Wetzel (1968). Because amino groups possess superior electron donor properties (Zabicky, 1968), DON containing tertiary amino groups, in particular, could be responsible for many DOM complexing responses known to suppress photosynthesis in hardwater lakes (Wetzel, 1969a).…”

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confidence: 99%

Interactions of dissolved and particulate nitrogen in lake metabolism

Manny¹

1971

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Weekly measurements of dissolved ammonia, nitrite, and nitrate for 22 months and organic nitrogen for 12 months were made in two hardwater lakes and seasonally in four other lakes representing a chemical and trophic spectrum in glaciated Michigan. Seston at 1 m depth was fractionated weekly for 14 months using 10 um Nitex netting in two lakes representing extremes of hardwater productivity.Net and nanno fractions were analyzed by micro-Kjeldahl digestion for organic nitrogen. Seasonal changes in all nitrogenous parameters were subsequently related to changes in fifteen other chemical and biological parameters assayed simultaneousl y.More than half of total sestonic pigments, algal cell volume, and organic nitrogen were present all year in the nannosestonic fraction in the unproductive and productive lake. These data supported the hypothesis that nannophytoplankton contain more nitrogen per unit cell volume than netphytoplankton. DISTRIBUT ION OF THIS DOCUMEN T IS UNLIMITEDfl DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document.

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confidence: 99%

Interactions of dissolved and particulate nitrogen in lake metabolism

Manny¹

1971

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“…The carbonyl group is a readily available building block for the synthesis of substituted alcohols . While the nucleophilic addition to the carbonyl group is favorable and widely studied, the radical addition to the carbonyl group is difficult, as the resulting alkoxyl radical undergoes β-fragmentation readily to reverse the reaction, especially for the radical addition to ketones (Scheme a) .…”

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Intermolecular Radical Addition to Ketoacids Enabled by Boron Activation

Xie

Huang

et al. 2019

J. Am. Chem. Soc.

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The intermolecular radical addition to the carbonyl group is difficult due to the facile fragmentation of the resulting alkoxyl radical. To date, the intermolecular radical addition to ketones, a valuable approach to construct quaternary carbon centers, remains a formidable synthetic challenge. Here, we report the first visible-lightinduced intermolecular alkyl boronic acid addition to αketoacids enabled by the Lewis acid activation. The in situ boron complex formation is confirmed by various spectroscopic measurements and mechanistic probing experiments, which facilitates various alkyl boronic acid addition to the carbonyl group and prevents the cleavage of the newly formed C−C bond. Diversely substituted lactates can be synthesized from readily available alkyl boronic acids and ketoacids at room temperature merely under visible light irradiation, without any additional reagent. This boron activation approach can be extended to alkyl dihydropyridines as radical precursors with external boron reagents for primary, secondary, and tertiary alkyl radical additions. The pharmaceutically useful anticholinergic precursors are easily scaled up in multigrams under metal-free conditions in flow reactors.T he carbonyl group is a readily available building block for the synthesis of substituted alcohols. 1 While the nucleophilic addition to the carbonyl group is favorable and widely studied, the radical addition to the carbonyl group is difficult, as the resulting alkoxyl radical undergoes βfragmentation readily to reverse the reaction, especially for the radical addition to ketones (Scheme 1a). 2 To date, the intermolecular radical addition to ketones, 3,4 which is valuable to construct quaternary carbon centers, 5 remains a formidable synthetic challenge. Lactates are important biological metabolites, which are precursors of poly-α-hydroxy acids for targeted drug delivery, 6 and include many prescription drugs such as anticholinergic Oxybutynin and Glycopyrrolate (see Scheme 3b for structures). 7 The α-ketoacid is a readily available synthetic building block to prepare lactates by nucleophilic additions with alkyllithiums or Grignard reagents. 8 However, these reactions are susceptible to air and moisture, and the strong nucleophilicity of these reagents unavoidably result in undesirable side reactions. 9 To this end, the new synthetic approaches to lactates, especially from different mechanistic manifolds, are in high demand.Ketoacids currently undergo decarboxylative acyl radical formations in radical reactions, and their engagement as the radical acceptors remains unknown (Scheme 1b). 10 Organoborons are environmentally friendly and readily available, and are stable synthetic building blocks with Lewis acidity. 11 In this communication, we report the first alkyl boronic acids radical addition to ketoacids with the Lewis acid activation from organoborons, which can be extended to alkyl dihydropyridine radical addition to ketoacids in the presence of external boron reagents (Scheme 1c).

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