Read e-book online Advances in Heterocyclic Chemistry, Vol. 94 PDF

By Alan R. Katritzky (ed.)

ISBN-10: 0123739632

ISBN-13: 9780123739636

Written via verified gurus within the box, the excellent experiences mix descriptive chemistry and mechanistic perception and yield an realizing of the way the chemistry drives the homes. quantity ninety four of Advances in Heterocyclic Chemistry commences with a assessment of cascade reactions on heterocyclic synthesis. The bankruptcy offers a desirable array of complicated sequences which supply effective routes to a large choice of heterocyclic platforms. the second one bankruptcy is the 12th within the sequence at the natural chemistry of heterocyclic ligands in steel complexes. the current contribution bargains with the chemistry of polypyridine ligands in organomanganese and organorhenium complexes. Its present value will be measured by way of the truth that, of the approximately seven-hundred references, nearly part date from the final 10 years. guidance of aminoisoxazoles and their software within the synthesis of condensed structures also are lined. within the ultimate bankruptcy, isothiazolium salts and their use in synthesis are reviewed. Many condensed S,N-heterocyclic platforms are defined during this, the 1st assessment devoted to this topic.
* updated ends up in the topic which maintains to realize significance and expand
* Makes on hand to graduate scholars and examine employees in educational and business laboratories the most recent studies on big range of heterocyclic topics
* The sequence types a truly massive database protecting large parts of heterocyclic chemistry

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K. BUR AND A. PADWA 36 N OMs H H N DIBAL-H CH2 [Sec. A CH2 H SiMe3 268 O 269 N O H MeO MeO MeO Si R N OMs HO NH DIBAL-H OMe MeO cephalotaxine CH2 CH2 271 270a R = Me 270b R = Ph Scheme 49 O Cl O O 272 Et N PMP PMP N O OEt + PMP N Cl −78 °C THF H N PMP 273 O O 20 °C PMP N OEt H N PMP 274 O 275 Scheme 50 IV. Cation-Promoted Cyclization Cascades A. NITROGEN STABILIZED CARBOCATIONS The Mannich reaction is a very common process that occurs in many tandem reaction sequences. For example, the Overman Aza-Cope cascade sequence is terminated by a Mannich reaction (cf.

Prolonged heating, however, led to the isolation of the cyclic thiourea 256b as a single stereoisomer in 89% yield. Several other examples, differing in the nature of the alkyl substituent, were also reported. C. OTHER REARRANGEMENTS In the context of developing rapid access to thioaurone structures, De and coworkers observed an interesting 6p-electrocyclization/isomerization cascade. The reaction of sulfanyl amide 257 with an excess of LDA and cinnamaldehyde produced thioaurone 258 in 83% yield (Scheme 47) (03SL1479).

The cascade was initiated by a [2,3]-rearrangement of the sulfoxide, which first produced the allene intermediate 214. A subsequent [3,3]rearrangement of the transient allene then gave enone 215. Tautomerization of the thione functionality afforded 216, and this was followed by intramolecular Michael addition to give the observed product 217. B. [3,3]-SIGMATROPIC REARRANGEMENTS Of the various heterocycle-forming cascade reactions involving [3,3]-rearrangements, Overman’s use of the Aza-Cope rearrangement/Mannich cyclization sequence certainly represents the best-known example of this methodology (88JA4329, 92ACR352).

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Advances in Heterocyclic Chemistry, Vol. 94 by Alan R. Katritzky (ed.)


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