Selenoaldehydes

from Wikipedia, the free encyclopedia
Selenoaldehydes
General structural formula of selenoaldehydes
The selenocarbonyl group is marked in blue . R = H, organic radical ( alkyl , aryl or the like).

Selenoaldehyde are organic , chemical compounds . They represent the selenium analogues of aldehydes and thioaldehydes and belong to the selenocarbonyl compounds .

The oxygen atom in its functional group has been replaced by a selenium atom. This is bound to the carbon by a double bond , which also binds a hydrogen atom . Selenoaldehydes are reactive and resemble thioaldehydes in their properties , but are more unstable. However, they can be stabilized thermodynamically or kinetically . Organic compounds containing selenium are often toxic , which makes research difficult. Selenoaldehydes are of little practical importance, but because of their reactivity they are used as intermediates in organic syntheses .

properties

Similar to thioaldehydes, selenoaldehydes polymerize and trimerize easily to 1,3,5-triselanes. The trimer of selenoacetaldehyde can occur in the α-form or in the β-form:

Isomerism of triselanes (here 2,4,6-trimethyl-1,3,5-triselanes)
trans or α form of 2,4,6-trimethyl-1,3,5-triselane
α-form		 cis or β form of 2,4,6-trimethyl-1,3,5-triselane
β-form

The α-form is preferably formed for steric reasons, but can be converted into the β-form by a reaction with silver nitrate and ammonia . Monomeric selenoaldehydes can be stabilized by heteroaromatic substituents or by conjugated , mesomeric systems, whereby the selenium atom can be included in the ring structure by mesomerism .

synthesis

Selenoaldehydes can be obtained from aldehydes . If z. B. Acetaldehyde is reacted with hydrogen selenide and hydrochloric acid , resulting in selenoacetaldehyde with elimination of water . This is unstable and can e.g. B. can be isolated as a Diels-Alder adduct with cyclopentadiene .

Synthesis of selenoacetaldehyde

The resulting heterocycles are very reactive. You will e.g. B. used to introduce selenium atoms into organic molecules. Cycloadditions of substituted selenoaldehydes can be controlled regioselectively. Cycloadditions of this type can also take place intramolecularly. The Wittig reaction with elemental selenium also leads to selenoaldehydes. Heteroaromatic Selenoaldehyde may be prepared by the Vilsmeier-Haack reaction with and subsequent treatment sodium selenide be synthesized. Current studies formulate the synthesis of selenoaldehydes ( 2 ) through the self- condensation of sterically demanding selenium analogues of aryl-substituted sulfenic acids ( 1 ), which proceeds autocatalytically :

Synthesis of selenoaldehydes from selenium analogues of alkanesulfenic acids

In addition, selenocarbonyl compounds can be produced with Woollins' reagent , which is the selenium-containing, analogous compound to Lawesson's reagent .

Reactions

Selenoaldehydes react as dienophiles in Diels-Alder reactions . In addition, they can function as starting materials in the diselenide synthesis. Due to their reactivity, selenoaldehydes react to form trimers and polymers .

Trimerization and polymerization of selenoformaldehyde

See also

Individual evidence

  1. ↑ a b c d Paulmier, C. (1986): Selenium Reagents and Intermediates in Organic Synthesis . 4th volume. Oxford: Pergamon Books. Pp. 58-63, ISBN 0-08-032484-3 .
  2. ↑ Okazaki, R., Kumon, N. & Inamoto, N .: 2, 4, 6-Tri-tert-butylselenobenzaldehyde, the first stable seleno aldehyde . Journal of the American Chemical Society , 1989 , 111 (15) , pp. 5949-5951, [1] .
  3. ↑ a b Guzirc, FS (1987): The Chemistry of Selenocarbonyl Compounds. In Liotta, D. (Ed.): Organoselenium Chemistry . New York: Wiley. Pp. 277-324, ISBN 0-471-88867-2 .
  4. ↑ Schönberg, A. & Wagner, A. (1955): Methods for the production and conversion of thioaldehydes and thioketones. In Müller, E. (Ed.): Methods of Organic Chemistry . Volume IX: sulfur, selenium, tellurium compounds. Stuttgart: Thieme Verlag. Pp. 1195-1199.
  5. ↑ Meinke, PT, & Krafft, GA: Synthesis and cycloaddition reactivity of selenoaldehydes . Journal of the American Chemical Society , 1988 , 110 (26) , pp. 8671-8679, doi: 10.1021 / ja00234a015 .
  6. ↑ Mikolajczyk, M., Drabowicz, J. & Kiełasiński, P. (1995): Formation of C-Se and C-Te Bonds. In Helmchen, G. et al. (Editor): Methods of Organic Chemistry: Stereoselective Synthesis . Volume E21e, Stuttgart: Thieme, pp. 5083-5132, ISBN 3-13-100124-0 .
  7. ↑ Degl'Innocenti, A. et al .: Silicon-Mediated Synthesis of Selenoaldehydes and Selenoacylsilanes and Their Hetero Diels – Alder Reactions . Phosphorus, Sulfur, and Silicon and the Related Elements, 2009 , 184 (6) , pp. 1621-1626, doi: 10.1080 / 10426500902947989 .
  8. ↑ Meinke, PT, & Krafft, GA: Regiochemical preferences in selenoaldehyde cycloadditions . Tetrahedron , 1987 , 28 (43) , pp. 5121-5124, doi: 10.1016 / S0040-4039 (00) 95607-7 .
  9. ↑ Segi, M. et al .: Intramolecular Diels-Alder reaction of selenoaldehydes . Tetrahedron , 1988 , 29 (52) , pp. 6965-6968, doi: 10.1016 / S0040-4039 (00) 88488-9 .
  10. ↑ Okuma, K. et al .: The Reaction of Wittig Reagents with Selenium. Formation of Selenoaldehyde . Bulletin of the Chemical Society of Japan , 1990 , 63 (6) , pp. 1653-1657, doi: 10.1246 / bcsj.63.1653 .
  11. ↑ Sase, S., Kakimoto, R. & Goto, K .: Synthesis of a Stable Selenoaldehyde by Self ‐ Catalyzed Thermal Dehydration of a Primary ‐ Alkyl ‐ Substituted Selenenic Acid , Angewandte Chemie International Edition , 2015 , 54 (3) , p . 901-904, doi: 10.1002 / anie.201409485 .
  12. ↑ Hua, G., & Woollins, JD: Synthesis and reactivity of phosphorus selenium rings . Angewandte Chemie , 2009 , 121 (8) , pp. 1394-1403, doi: 10.1002 / anie.200800572 .
  13. ↑ Li, GM, Segi, M., & Nakajima, T .: α, β-Unsaturated selenoaldehydes and selenoketones the reaction behavior as a heterodiene and / or a dienophile . Tetrahedron , 1992 , 33 (24) , pp. 3515-3518, doi: 10.1016 / S0040-4039 (00) 92677-7 .
  14. ↑ Krafft, GA, & Meinke, PT: Selenoaldehydes: preparation and dienophilic reactivity . Journal of the American Chemical Society , 1986 , 108 (6) , pp. 1314-1315, doi: 10.1021 / ja00266a041 .