Crotyl group

Crotyl groups attached to R.

A crotyl group is an organic functional group with the formula RCH2CH=CHCH3. Systematically, it is called a but-2-en-1-yl group and exhibits geometric isomerism, being either cis (Z) or trans (E). There are many simple compounds in which the crotyl group forms base carbon chain: crotyl alcohol, crotonaldehyde, crotonic acid, and crotyl acrylate are examples.

Synthesis of crotylates

Crotylate (crotyl anions) can be synthesised from 2-butene (either isomer) by deprotonation with highly basic organometallic reagents, typically organolithium reagents. The negative charge is delocalised over three of the carbon atoms of the crotylate group.

Crotylation reactions

Crotyl halides, crotyl alcohols, crotyl silanes, crotonaldehyde and crotyl boronates are useful reagents for synthesizing crotyl and allyl compounds. Crotyl and allyl compounds are common intermediates in total synthesis due to their ability to undergo sigmatropic rearrangements.

Crotylboronates are easily made from reaction of crotyl anions with alkoxy boronates, and are useful reagents in the formation of crotyl and allyl alcohols.

Trans-crotonaldehyde is commonly used to determine the effective Lewis acidity of Lewis acids, determined from the change in 1H NMR shift of the crotonaldehyde handle on binding to a Lewis acid. Limitations of the method include secondary interactions to the 1H NMR handle obscuring the true effect of the Lewis acid, and weak donor strengths of trans-crotonaldehyde resulting in incomplete Lewis acid-base adduct formation.

References

  1. ↑ "crotyl". Merriam-Webster.com Dictionary. Merriam-Webster. OCLC 1032680871.
  2. 1 2 Helmboldt, Hannes; Köhler, Daniel; Hiersemann, Martin (2006-04-01). "Synthesis of the Norjatrophane Diterpene (−)-15-Acetyl-3-propionyl- 17-norcharaciol". Organic Letters. 8 (8): 1573–1576. doi:10.1021/ol060115t. ISSN 1523-7060.
  3. 1 2 3 Batey, Robert A.; Thadani, Avinash N.; Smil, David V. (1999-07-01). "Potassium allyl- and crotyltrifluoroborates: Stable and efficient agents for allylation and crotylation". Tetrahedron Letters. 40 (23): 4289–4292. doi:10.1016/S0040-4039(99)00774-1.
  4. ↑ Dolgoplosk, B.A.; Beilin, S.I.; Vollershtein, E.L.; Teterina, M.P. (1975-03-25). "Studies of crotyl anion reactions and some regularities of copolymerization in hexamethylphosphortriamide". European Polymer Journal. 11 (3): 287–291. doi:10.1016/0014-3057(75)90078-6.
  5. ↑ O'Hora, Paul S.; Incerti‐Pradillos, Celia A.; Kabeshov, Mikhail A.; Shipilovskikh, Sergei A.; Rubtsov, Aleksandr E.; Elsegood, Mark R. J.; Malkov, Andrei V. (2015-03-16). "Catalytic Asymmetric Crotylation of Aldehydes: Application in Total Synthesis of (−)‐Elisabethadione". Chemistry – A European Journal. 21 (12): 4551–4555. doi:10.1002/chem.201500176. ISSN 0947-6539.
  6. ↑ Arefolov, Alexander; Panek, James S. (2005-04-01). "Crotylsilane Reagents in the Synthesis of Complex Polyketide Natural Products: Total Synthesis of (+)-Discodermolide". Journal of the American Chemical Society. 127 (15): 5596–5603. doi:10.1021/ja043168j. ISSN 0002-7863.
  7. ↑ Lachance, Hugo; Lu, Xiaosong; Gravel, Michel; Hall, Dennis G. (2003-08-01). "Scandium-Catalyzed Allylboration of Aldehydes as a Practical Method for Highly Diastereo- and Enantioselective Construction of Homoallylic Alcohols". Journal of the American Chemical Society. 125 (34): 10160–10161. doi:10.1021/ja036807j. ISSN 0002-7863.
  8. ↑ Tan, Qiuyuan; Wang, Xinqiao; Xiong, Yang; Zhao, Zimeng; Li, Lu; Tang, Pei; Zhang, Min (2017-04-18). "Chiral Amino Alcohol Accelerated and Stereocontrolled Allylboration of Iminoisatins: Highly Efficient Construction of Adjacent Quaternary Stereogenic Centers". Angewandte Chemie International Edition. 56 (17): 4829–4833. doi:10.1002/anie.201700581. ISSN 1433-7851.
  9. ↑ Childs, Ronald F.; Mulholland, D. Lindsay; Nixon, Alan (1982-03-15). "Lewis acid addticts of α,β-unsaturated carbonyl and nitrile compounds. A calorimetric study". Canadian Journal of Chemistry. 60 (6): 809–812. doi:10.1139/v82-118. ISSN 0008-4042.
  10. ↑ Erdmann, Philipp; Schmitt, Manuel; Janus, Lara; Greb, Lutz (2025-02-17). "Critical Evaluation of Childs Method for the NMR Spectroscopic Scaling of Effective Lewis Acidity: Limitations and Resolution of Earlier Discrepancies". Chemistry – A European Journal. 31 (10). doi:10.1002/chem.202404181. ISSN 0947-6539.