Recovery

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The Three Rs of Green Chemistry

• Recovery
• Isolation of solvents and reagents following the
  completion of reaction
• Reuse/Recycling
• Beneficial both environmentally and economically
• Regeneration
• Able to be regenerated with high efficiency

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Principles of Green Chemistry

• Prevent waste
• Better to prevent waste than to dispose of it
• Less hazardous reaction conditions
• More amenable to undergraduate instruction
• More focus on the reaction and products than
  complex procedures
• Safer solvents

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HMBI vs. HTIB
Hydroxy(tosyloxy)iodobenzene Kosers
Reagent HTIB A mild and useful oxidant that
mimics elemental bromine 277 publications MW
392.22 g/mol
1H-1-hydroxy-5-methyl-1,2,3-benziodoxathiole
3,3-Dioxide HMBI Should be a compact
heterocyclic equivalent 3 publications MW
314.10 g/mol
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Typical reaction of HTIB

• Xie, Y.Y. and Z.C. Chen, Synth. Comm. 2002, 32,
  1875-1879

Will HMBI react similarly?
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Goals of the Projects

• We wish to investigate if HMBI is a true analog
  of HTIB using a simple model reactions
• Demonstrate of the generality of any reactions
  through exploration of substrates
• To employ more modern, microscale work-up
  procedures to reduce waste and ease purification
• Demonstrate the recovery and recycling of the
  reagent

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Experimental Procedure

• With our new NMR only small scale (0.5 mmol)
  reactions need to be run to probe these reactions

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Experimental Procedure

• Small scale extraction techniques are used to
  maximize yield
• Specialized glassware is also used for filtration
  and drying operations

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Experimental Procedure

• Preparative TLC allows a full analysis of all
  reaction products we only need 1-5 mg to
  acquire a good 1H NMR!

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Experimental Procedure

• Can the reagent be recycled and reused?
• If the aqueous layer from the extraction
  technique is allowed to evaporate reduced HMBI
  could be recovered quantitatively (95)

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• Example 1
• Oxidative rearrangements of arylalkenes to
  arylalkanones
• The purpose of this project is to make this known
  reaction green in two ways. First, replacing
  the original reagent hydroxyl(tosyloxy)iodobenze
  ne (HTIB) with an analog that allows the reduced
  by-product to be separated from the reaction
  mixture by simple aqueous extraction for
  re-oxidation and reuse. Second, because
  iodobenzene is no longer contaminating the
  organic by-products of the reaction, column
  chromatography can either be simplified or
  eliminated altogether.

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• Example 2
• Oxidative Rearrangement of alkynes with CHTIB
• HTIB can oxidize terminal and internal alkynes
  (terminal shown) in various solvents one of the
  more interesting oxidative rearrangements is
  observed when terminal alkynes are treated in an
  alcohol, to afford alkyl esters

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• Example 3
• Synthesis of Isoflavones Currently underway
• Isoflavones are recognized as potent
  anti-oxidants and phytoestrogens. Most syntheses
  in the literature rely on toxic thallium(III)
  compounds
• We have developed a synthesis of isoflavones that
  is basically one step from easily prepared
  2-hydroxychalcones

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• Example 4
• Conversion of carboxamides to N-acetylamines
• We have developed a synthesis of isoflavones that
  is basically one step from easily prepared
  2-hydroxychalcones