eprintid: 25965
rev_number: 11
userid: 4899
dir: disk0/00/02/59/65
datestamp: 2015-09-09 13:27:03
lastmod: 2016-11-15 14:29:57
status_changed: 2015-09-09 13:27:03
type: thesis_degree
metadata_visibility: show
contact_email: amb305@pitt.edu
item_issues_count: 0
eprint_status: archive
creators_name: Berne, Alexander M
creators_email: amb305@pitt.edu
creators_id: AMB305
title: A Formal Vinyl Sulfonyl Nazarov Cyclization Accesses 9-(tosylmethyl)-2,3,4,4a-tetrahydro-1H-fluorenes
ispublished: unpub
divisions: sch_as_chemistry
full_text_status: public
keywords: Nazarov, cyclization, dienyl sulfone, vinyl sulfone, allyl sulfone, tetrahydrofluorene, cyclobutene, electrocyclic ring opening, electrocyclization 
abstract: During the course of a proposed route to synthesize ladderane lipids, a novel one-pot 4π electrocyclic ring opening followed by a Nazarov-type 4π electrocyclization reaction was discovered. The reaction was studied further due to its potential as a method for accessing the privileged tetrahydrofluorene scaffold and the opportunities for further functionalization provided by the allyl sulfone moiety. Optimized conditions for the transformation involved refluxing model substrate 7-phenyl-8-tosylbicyclo[4.2.0]oct-6-ene in 1,2-dichloroethane for 3 h to generate intermediate (E)-1-((2-(cyclohex-1-en-1-yl)-2-phenylvinyl)sulfonyl)-4-methylbenzene. Upon cooling to room temperature, addition of 1.2 equiv iron(III) chloride promotes cyclization to furnish 9-(tosylmethyl)-2,3,4,4a-tetrahydro-1H-fluorene after 10 h in 78% yield. In order to determine the effect electronics may have on the transformation, functionality was introduced onto the phenyl ring. While no noticeable effect was observed on the electrocyclic ring opening step, the nature of the substituents significantly affected the quantity of promoter required for the cyclization step. Although a superstoichiometric amount of iron(III) chloride and heat was required with an electron withdrawing substituent on the aryl ring, electron donating substituents lowered the activation barrier to cyclization – necessitating only catalytic amounts of iron(III) chloride at room temperature. This transformation represents the first report of a Nazarov cyclization with a vinyl sulfone on the central carbon.   
date: 2015-09-09
date_type: published
pages: 215
institution: University of Pittsburgh
refereed: TRUE
etdcommittee_type: committee_member
etdcommittee_type: committee_member
etdcommittee_type: committee_chair
etdcommittee_name: Curran, Dennis P
etdcommittee_name: Floreancig, Paul E
etdcommittee_name: Brummond, Kay M
etdcommittee_email: curran@pitt.edu
etdcommittee_email: florean@pitt.edu
etdcommittee_email: kbrummon@pitt.edu
etdcommittee_id: CURRAN
etdcommittee_id: FLOREAN
etdcommittee_id: KBRUMMON
etd_defense_date: 2015-05-28
etd_approval_date: 2015-09-09
etd_submission_date: 2015-08-12
etd_release_date: 2015-09-09
etd_access_restriction: immediate
etd_patent_pending: FALSE
thesis_type: thesis
degree: MS
citation:   Berne, Alexander M  (2015) A Formal Vinyl Sulfonyl Nazarov Cyclization Accesses 9-(tosylmethyl)-2,3,4,4a-tetrahydro-1H-fluorenes.  Master's Thesis, University of Pittsburgh.    (Unpublished)  
document_url: http://d-scholarship-dev.library.pitt.edu/25965/1/Final_MS_Thesis_Alex_Berne.pdf