Bardhan-Sengupta synthesis

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The Bardhan-Sengupta synthesis is a name reaction from the field of organic chemistry . The reactions were named after the chemist Jogendra Chandra Bardhan (1896–1964) from what is now Bangladesh and his then PhD student Suresh Chandra Sengupta. named and enables the synthesis of phenanthrene from an alcohol.

Overview reaction

The phenanthrene synthesis proceeds according to the following scheme:

Bardhan-Sengupta overview reaction

Phosphorus pentoxide can be used to produce the fully flavored phenanthrene from an alcohol via cyclization and subsequent dehydrogenation using selenium.

Reaction mechanism

The reaction mechanism presented below is described in the literature, but has not yet been fully scientifically proven:

Proposed reaction mechanism Bardhan – Sengupta synthesis

By protonation (e.g. with phosphoric acid) or by phosphorylation with phosphorus pentoxide of the alcohol ( 1 ), the carbocation ( 2 ) is formed with elimination of water . By means of electrophilic aromatic substitution , ring closure occurs ( 3 ) and, associated with this, deprotonation ( 4 ). The addition of selenium at high temperatures eventually leads to multiple dehydration , resulting in the fully flavored phenanthrene ( 5 ).

Due to the toxic effects of selenium, other substances are now used to dehydrate compound 4 . Possible examples are platinum, palladium, nickel or sulfur.

Individual evidence

  1. ↑ RN Chakravarti: Jogendra Chandra Bardhan , Indian National Science Academy, accessed March 6, 2018.
  2. ^ S. Chakraborty and C. Saha: A Tribute to Bardhan and Sengupta. In: Resonance. 20, 2015, pp. 628-642, doi: 10.1007 / s12045-015-0221-4 .
  3. ↑ Jogendra C. Bardhan and Suresh C. Sengupta: Resin acids. Part I. Synthesis of phenanthrene hydrocarbons derived from d-pimaric acid, and a new route to phenanthrene. In: Journal of the Chemical Society. 1932, pp. 2520-2526, doi: 10.1039 / JR9320002520 .
  4. ↑ Alfred Hassner and Irishi Namboothiri: Organic Synthesis Based on Reaction name , Elsevier, 2012, ISBN 978-0-08-096630-4 , p. 30
  5. ↑ a b c Jie Jack Li: Name Reactions for Carbocyclic Ring Formations , Wiley, 2010, ISBN 978-0-47-008506-6 , doi: 10.1002 / 9780470872215 pp. 198-208.