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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Annulation and cycloaromatization reactions of 3-aryl (alkyl) thio-1-trimethylsiloxy-1-methoxy-1,3-butadienes

Prasad, Chaturvedula V. January 1986 (has links)
The title compounds were synthesized from methyl 3-aryl(alkyl)thio crotonic acids by deprotonation followed by silylation. The reactions of dienes with a number of carbonyl electrophiles under Lewis-acid catalysed conditions were investigated. The dienes exclusively give $ gamma$-alkylated products. The thio substituent enhances the $ gamma$-selectivity. / The reactions of dienes with a number of 1,3-dicarbonyl equivalents have been studied and a cycloaromatization reaction has been developed for the regiocontrolled synthesis of aryl sulfides in a 3C + 3C combination. The role of dienes in Diels-Alder reactions has also been investigated. / A new 4C + 2C annulation reaction has been developed based on the propensity of dienes to undergo Michael reaction with $ alpha$,$ beta$-unsaturated ketones under Lewis-acid catalysed conditions. These Michael adducts in turn were cyclized either with potassium tert-butoxide or with lithium thiophenoxide. Further, the tandem Michael-Claisen annulation reaction can be controlled to give either cis- or trans-fused 9-methyldecalin system with three carbonyl groups which are differently masked. The chemoselective transformations of the carbonyl groups were also described.
2

Studies and applications of intermolecular (4+3) cycloaddition reactions of epoxy and aziridinyl enolsilanes

Lam, Yan-yu, Sarah, 林恩如 January 2013 (has links)
published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy
3

Ring expansion reaction via homolytic pathways

Robertson, Jeremy January 1990 (has links)
The preparation of carbocyclic medium rings by two electron processes is reviewed with particular reference to the synthesis of natural products. The formation of medium rings by oxidative and homolytic methods is also reviewed. The synthesis and behaviour of both cis- and tran- ring expansion precursors is described. The 1,4-addition of tributylstannyl lithium to a range of cyclic α,β-unsaturated ketones was performed and procedures found whereby the so-formed enolates could be alkylated with a variety of electrophiles. Using these procedures a range of trans- ring expansion precursors were obtained in moderate to good yield. By the 1,4-addition of tributylstannyl lithium to 2-(ω-phenylselenoalkyl)-cyclohexenones, followed by enolate quenching with either water or methyl iodide, a range of cis- ring expansion precursors were produced. Homolytic ring expansion by either one, three, or four carbon atoms was shown to be possible, producing, respectively, seven, nine, or ten membered functionalised cycloalkenones in high yield except in cases where intramolecular reductive elimination was also possible. Attempts to extend this methodology to the synthesis of exomethylene cycloalkanones is described. The 3-tributylstannyl-3-(ω-phenylselenoalkyl)-cyclohex-2-enone precursors were found not to be successful substrates for ring expansion. The regiospecific alkylation of 2-(tributylstannylmethyl)-cyclohexanone with l-chloro-4-iodo-butane, followed by conversion of the chloride moiety to iodide led to a precursor which, on exposure to homolysis conditions, fragmented to produce the desired exomethylene cyclodecanone in high yield. Work directed towards the synthesis of medium ring cycloalkynones is described. Procedures were developed whereby 2-alkylated cyclohexan-l,3-dione derivatives could be obtained cleanly and in excellent yield on a large scale. The conversion of these derivatives to potential cycloalkynone precursors is described. It is shown that the products obtained after exposure of these precursors to homolysis conditions could, in principle, be derived from the putative cycloalkynones and mechanisms are suggested to explain the formation of these compounds. The homolytic ring expansion reaction was also performed on a substrate possessing an acyl radical precursor in the hope that a medium ring 1,2-dione would be produced. The synthesis of this substrate and its behaviour towards ring expansion is described. It is shown that, again, radical reaction was successful (to the medium ring dione) however subsequent reactions of this product led to the isolation and characterisation of a number of compounds . Attempts to extend this methodology to the synthesis of the natural products curdione and neocurdione is also described. Model reactions with 2,6-dimethylcyclohex-2-enone as the 1,4-addition precursor and 1,4-di-iodobutane as the electrophile led to a ring expansion substrate which fragmented to two ring contracted isomeric compounds in addition to the ring expanded material. Approaches to the preparation of suitable electrophiles for the natural product synthesis are described and their proposed use in subsequent conversion to curdione and neocurdione given.
4

Part I, Interrupted Nazarov cyclization on silica gel: Part II, Tandem alkylation-cyclization process via an O,C dianion

Dhoro, Francis January 2006 (has links)
Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (p. 63). / xi, 101 leaves, bound ill. 29 cm
5

Stereochemical aspects of the cycloheptane ring

Engle, John Edward 12 1900 (has links)
No description available.
6

Chemical and photochemical studies relating to small rings

Andrews, S. D. January 1967 (has links)
No description available.
7

Conformational effects in cyclohexane derivatives

Schofield, John D. January 1970 (has links)
No description available.
8

Alkylation of furan with 2-phenylthioallyl chloride

Gains, Lawrence Howard, 1948- January 1977 (has links)
No description available.
9

The attempted synthesis of bicyclo [2.2.0] HEX-2-ENE and cyclobutene by the Ramberge-Backlund reaction

Cole, Harlie David January 2010 (has links)
Digitized by Kansas Correctional Industries
10

Annulation and cycloaromatization reactions of 3-aryl (alkyl) thio-1-trimethylsiloxy-1-methoxy-1,3-butadienes

Prasad, Chaturvedula V. January 1986 (has links)
No description available.

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