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New technologies for constructing C-C, C-N, and C-S bonds

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Call No.	QD47.5.N43 D3 2012rob
Author	Robertson, Forest James.
Title	New technologies for constructing C-C, C-N, and C-S bonds
Date	2012
Abstract	I. Intermolecular C-S Bond Forming Reactions The relatively small number of efficient C-S bond forming reactions in the literature prompted an investigation into the synthesis of allylic thioethers. The technology that we developed allowed us, in two steps, to control each C-S bond forming event starting from two alcohols, which was a significant improvement on current methods. Under photochemical conditions, allylic alcohols/ethers were converted to their corresponding phosphorothioate esters, and then treated with an exogenous alkoxide source to form the allylic thioethers. Furthermore, the second C-S bond forming event was shown to be stereospecific. This reaction was quite general, and amenable to a variety of alcohols (e.g. alkyl, aryl, heteroaryl). II. Intramolecular C-S Bond Forming Reactions As an extension of the allylic thioether methodology, an asymmetric synthesis of 2-aryl substituted tetrahydrothiophenes was developed. The appealing aspect of this methodology was the utilization of a common starting material, which contained both the phosphorothioate ester and Weinreb amide functionality. Addition of various Grignard reagents to the common starting material provided the corresponding aryl/heteroaryl ketones, which were then reduced in an asymmetric fashion using the CBS catalyst, and then cyclized to afford the chiral tetrahydrothiophenes (THTs) using NaH. This reaction provided chiral THTs in good to excellent yields, and enantioselectivities of up to 97% ee. This methodology was amenable to various heteroaryl and 2-, 3-, and 4-substituted aryl substrates (e.g. amide, ester, ketal, nitrile). III. Br�nsted Acid-Catalyzed C-C/C-N Bond Forming Reactions A facile method for the synthesis of 5,6-fused indoline aminals, which is the highly unusual structural moiety found in the communesin family of natural products, has been developed. Aza o-quinone methides are labile intermediates, generated from 2-aminobenzyl derivatives via installment of a leaving group (e.g. halogen, carbonate, aziridine), that other research groups have trapped with various nucleophiles to form the desired product. In this method, 2-aminobenzyl alcohols were treated with various Lewis and Br�nsted acids to generate the corresponding aza o-quinone methides without any need for pre-activation of the alcohol; however, TFA was shown to be optimal for this process. The aza o-quinone methides were trapped with a variety of indoles to form the expected, tetracyclic products in good yields. Appealing aspects of this method include the mild reaction conditions, and not having to activate the substrates to achieve reactivity. This method was also applied to the alkylation of indoles, and it was shown to be a very mild and effective means for performing this transformation.
Description	xiii, 334 leaves : ill. (some col.) ; 28 cm.
Format	application/pdf
Advisor	Wu, Jimmy; Glueck, David S; Wilcox, Dean E; Block, Eric
College	Dartmouth College -- Department of Chemistry.
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D.)--Dartmouth College.
Copyright	All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means without permission in writing from the author.
DOI	http://dx.doi.org/10.1349/ddlp.410

Title	Page 1
Format	application/pdf
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D.)--Dartmouth College.
Full Text	NEW TECHNOLOGIES FOR CONSTRUCTING C–C, C–N, AND C–S BONDS A Thesis Submitted to the Faculty in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry by Forest James Robertson DARTMOUTH COLLEGE Hanover, New Hampshire May 11th 2012 Examining Committee: (chair) Jimmy Wu David S. Glueck Dean E. Wilcox Eric Block Brian W. Pogue, Ph.D. Dean of Graduate Studies

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New technologies for constructing C-C, C-N, and C-S bonds

New technologies for constructing C-C, C-N, and C-S bonds