The chain extension of beta-keto phosphonates and the synthesis of polycyclopropanes

A series of beta-keto phosphonates was prepared and their reactivity with the Furukawa-modified Simmons-Smith zinc carbenoid was studied. Various functionality was incorporated into these molecules in efforts to broaden the scope of the zinc-mediated chain extension reaction. The mechanism of the chain extension of dimethyl (2-oxopropyl)phosphonate was probed by nuclear magnetic resonance in efforts to observe key intermediates of these reactions. The stereochemistry of bis-, tris-, and tetrakis-cyclopropanes was confirmed by a one directional asymmetric independent synthesis. Application of an olefin cross-metathesis reaction allowed vinyl tetrakis-cyclopropane to be elaborated into an advanced intermediate toward the preparation of FR-900848, a polycyclopropanated natural product displaying desirable biological activity. The application of olefin metathesis chemistry represents both a novel and efficient means of incorporating both the intervening E-olefin and sequestered cyclopropane contained within these compounds

[18F]fluorination/decarbonylation: New route to aryl [18F]fluorides

A new route to aryl [18F]fluorides without electron withdrawing ring substituents has been developed. [18F]Fluorobenzaldehydes, prepared from no-carrier-added (NCA) [18F]fluoride using nucleophilic aromatic substitution of fluoro or nitro groups, were decarbonylated using palladium on charcoal (Pd-C). By this approach 2-methoxy-4-nitrobenzaldehyde was converted to NCA 3-[18F]fluorophenol (25-30%, EOB) and 4-fluoro-2-methoxy-5-methylbenzaldehyde to carrier-added (CA) 3-[18F]fluoro-4-methylphenol (30-40%, EOB). Overall synthesis time was about 2 h. Since the 4-fluoro-2-methoxy-5-methylbenzaldehyde was in turn prepared by methylation and regiospecific formylation of 3-fluoro-4-methylphenol, the overall process represents use of a removable activating group for nucleophilic aromatic substitution with [18F]fluoride for preparation of CA and NCA aryl [18F]fluorides.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29665/1/0000754.pd

Preparation and regioselectivity of simple sulfur and selenium substituted dienes in the Diels-Alder reaction, Part I Synthesis of macrocyclic polydentate ligands by successive michael additions to activated acetylenes, Part II

Ph.D.Charles L. Liott

The rhetoric of antecedence: Latin in middle English poetry

Bibliography: p. 251-272.Much English writing of the later fourteenth century incorporates a Latin presence. Latin may appear within the English text overtly, in direct quotation, or it may be introduced somewhere on a continuum of distance that ranges from close translation through allusion to announced reduction or omission of an antecedent Latin text. Making reference to selected works of Middle English prose and poetry, the dissertation looks at how English writers exploit the resources of both Latin and their own vernacular, developing what is termed a rhetoric of antecedence. At the level of style, the English authors use devices such as translation, allusion, interlingual word-play and the twin techniques of amplificatio and abbreviatio to appropriate elements of Latin texts and reposition them in their own, drawing on the expressive capacities of both linguistic universes. At the level of content, they identify the presence of antecedent Latin texts through various strategies then treat the intertextual relationship as a rhetorical place of invention, a place in which the authority of the antecedent Latin text becomes subject to inquiry and revision. Chapter One surveys attitudes to the Latin and English languages expressed in prefaces to English prose works of translation, then discusses Patience as an example of how close translation of an antecedent Latin text, influenced by its accompanying glosses and commentaries, makes possible the creation of an amplifying vernacular poem. Two chapters study Latin in Piers Plowman, the first treating aspects of macaronic style and the second treating passages in which the poet turns the space between his two working languages into a generative rhetorical locus. A final chapter comments on Chaucer's attitude to Latin textual antecedence, concluding with a study of literary ecphrasis in The House of Fame

Preparation of γ-Keto Phosphonates via a Zinc-carbenoid Chain Extension Reaction

A variety of β-keto phosphonates can be converted to γ-keto phosphonates through reaction with ethyl(iodomethyl)zinc. The presence of α-alkyl substituents, Lewis basic functionality, and modestly acidic NH-protons are accommodated in substrates of this reaction. Chain extension of β-keto phosphonates that contained olefinic functionality proceeded more quickly than cyclopropanation; however, it was not possible to effect the chain extension to the exclusion of cyclopropane formation. A primary reason for this imperfect chemoselectivity appears to be the slow chain extension of β-keto phosphonates. Nevertheless, the simplicity, the scope, and efficiency of this method serve to make it an attractive alternative to the established methods for γ-keto phosphonate formation