Hafnium trifluoromethanesulfonate

Hafnium(IV) triflate

Names
IUPAC name Hafnium(IV) trifluoromethanesulfonate
Identifiers
CAS Number	161337-67-3  Y
3D model (JSmol)	Interactive image
ChemSpider	21170913
EC Number	624-948-5
PubChem CID	9853707
CompTox Dashboard (EPA)	DTXSID201336882
InChI InChI=1S/4CHF3O3S.Hf/c4*2-1(3,4)8(5,6)7;/h4*(H,5,6,7);/q;;;;+4/p-4 Key: BQYMOILRPDTPPJ-UHFFFAOYSA-J
SMILES C(F)(F)(F)S(=O)(=O)[O-].C(F)(F)(F)S(=O)(=O)[O-].C(F)(F)(F)S(=O)(=O)[O-].C(F)(F)(F)S(=O)(=O)[O-].[Hf+4]
Properties
Chemical formula	Hf(OTf)4
Molar mass	774.8 g/mol
Appearance	Colourless solid
Melting point	350 °C (662 °F; 623 K)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	irritantant
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314, H315, H319, H335
Precautionary statements	P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
Flash point	Non-flammable
Safety data sheet (SDS)
Related compounds
Other anions	Hafnium tetrachloride Hafnium tetrafluoride Hafnium(IV) bromide Hafnium(IV) iodide
Other cations	Titanium(IV) triflate Zirconium(IV) triflate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y  verify  (what is  YN ?) Infobox references

Hafnium(IV) triflate or hafnium trifluoromethansulfonate is a salt with the formula Hf(OSO₂CF₃)₄, also written as Hf(OTf)₄. Hafnium triflate is used as an impure mixture as a catalyst. Hafnium (IV) has an ionic radius of intermediate range (Al < Ti < Hf < Zr < Sc < Ln) and has an oxophilic hard character typical of group IV metals. This solid is a stronger Lewis acid than its typical precursor hafnium tetrachloride, HfCl₄, because of the strong electron-withdrawing nature of the four triflate groups, which makes it a great Lewis acid and has many uses including as a great catalyst at low Lewis acid loadings for electrophilic aromatic substitution and nucleophilic substitution reactions. ^[1]

Preparation

The compound was first synthesized by the Kobayashi group in 1995 via the reaction of HfCl₄ and triflic acid. ^[2] This solid is air stable, easy to handle, and commercially available. ^[3]

Uses

Electrophilic Substitutions

Hf(OTf)₄ catalyzed Friedel-Craft acylation and alkylation reactions

Friedel-Craft acylation or alkylation reactions are some of the most important synthetic methodologies to introduce carbonyl or alkyl groups onto aromatic compounds. ^[4] The first Hf(OTf)₄ catalyzed Friedel-Crafts acylation was developed by Kobayashi et al. in 1995. ^{[2] [5]} The authors demonstrated that Friedel-Crafts acylation could be achieved in excellent yield between arenes and acid anhydrides when utilizing Hf(OTf)₄ as a catalyst. Hf(OTf)₄, was the most effective in comparison to other Lewis acids including BF₃ • OEt₂ , Sc(OTf)₃, and Zr(OTf)₄. Similalrly, Hf(OTf)₄ shows excellent activity in Friedel-Crafts alkylation's, and enabled the alkylation of benzene with benzylic and tertiary alkyl chlorides.

Hf(OTf)₄-catalyzed Friedel-Crafts alkylation has been utilized in the total synthesis of the altertoxin III framework. This approach provided a more efficient synthesis of the fused-ring structure compared to previous methods. ^[6]

Hf(OTf)₄ mediated synthesis of altertoxins

Hf(OTf)₄, alongside Sc(OTf)₃ and In(OTf)₃, has been shown to activate alkynes and enable electrophilic substitution. In 2004 Song and Lee et al. reported Hf(OTf)₄-catalyzed Friedel-Crafts alkenylation of benzene with alkenyl derivatives. ^[7]

Hf(OTf)₄ enabled electrophilic substitution of alkynes

Nucleophilic Substitutions

In 2008, Zhu et al. demonstrated that Hf(OTf)₄ was an effective catalyst for the thioacetalization of aldehydes and ketones. ^[8] In the absence of Lewis acid this reaction can occur in glycerol at 90 °C. Hf(OTf)₄ accelerated the reaction rate under milder conditions with only 0.1 mol% catalyst loading. For example, Hf(OTf)₄ catalyzes the reaction between benzaldehyde and 2.0 equiv. of either ethanethiol or 1.0 equiv. of propane-1,3,-dithiol readily in quantitative yield.

Hf(OTf)₄ catalyzed thioacetalization of benzaldehyde

This methodology was utilized in the total synthesis of (-)-leucomidine B from an enantioenriched monoacid synthesized via a Hf(OTf)₄ catalyzed thioacetalization. ^[9]

Total synthesis of (-)-leucomidine B

In 2009, Nakamura et al. demonstrated that Hf(OTf)₄ was uniquely able to catalyzed a Prins reaction between an aryl aldehyde and an O-protected/unprotected cyclohex-3-ene-1,2-dimethanol. ^[10]

Hf(OTf)₄ catalyzed Prins cyclization

References

1. Ishitani, Haruro; Suzuki, Hirotsugu; Saito, Yuki; Yamashita, Yasuhiro; Kobayashi, Shū (2015). "Hafnium Trifluoromethanesulfonate [Hf(OTf)4] as a Unique Lewis Acid in Organic Synthesis" . European Journal of Organic Chemistry. 2015 (25): 5485–5499. doi:10.1002/ejoc.201500423. ISSN   1099-0690.
2. Hachiya, Iwao; Moriwaki, Mitsuhiro; Kobayashi, Shu (1995-07-01). "Hafnium(IV) Trifluoromethanesulfonate, An Efficient Catalyst for the Friedel–Crafts Acylation and Alkylation Reactions" . Bulletin of the Chemical Society of Japan. 68 (7): 2053–2060. doi:10.1246/bcsj.68.2053. ISSN   0009-2673.
3. Li, Zhiya; Plancq, Baptiste; Ollevier, Thierry (2011), "Hafnium(IV) Trifluoromethanesulfonate" , Encyclopedia of Reagents for Organic Synthesis, American Cancer Society, doi:10.1002/047084289x.rn01315, ISBN   978-0-470-84289-8 , retrieved 2021-06-12
4. Calloway, N. O. (1935-12-01). "The Friedel-Crafts Syntheses" . Chemical Reviews. 17 (3): 327–392. doi:10.1021/cr60058a002. ISSN   0009-2665.
5. Hachiya, Iwao; Moriwaki, Mitsuhiro; Kobayashi, Shu (1995-01-16). "Catalytic Friedel-Crafts acylation reactions using hafnium triflate as a catalyst in lithium perchlorate-nitromethane" . Tetrahedron Letters. 36 (3): 409–412. doi:10.1016/0040-4039(94)02221-V. ISSN   0040-4039.
6. Geiseler, Oliver; Müller, Monika; Podlech, Joachim (2013-05-06). "Synthesis of the altertoxin III framework" . Tetrahedron. 69 (18): 3683–3689. doi:10.1016/j.tet.2013.03.013. ISSN   0040-4020. S2CID   93455317.
7. Song, Choong Eui; Jung, Da-un; Choung, Su Yhen; Roh, Eun Joo; Lee, Sang-gi (2004). "Dramatic Enhancement of Catalytic Activity in an Ionic Liquid: Highly Practical Friedel–Crafts Alkenylation of Arenes with Alkynes Catalyzed by Metal Triflates" . Angewandte Chemie International Edition. 43 (45): 6183–6185. doi:10.1002/anie.200460292. ISSN   1521-3773. PMID   15549737.
8. Wu, Yan-Chao; Zhu, Jieping (2008-12-05). "Hafnium Trifluoromethanesulfonate (Hafnium Triflate) as a Highly Efficient Catalyst for Chemoselective Thioacetalization and Transthioacetalization of Carbonyl Compounds" . The Journal of Organic Chemistry. 73 (23): 9522–9524. doi:10.1021/jo8021988. ISSN   0022-3263. PMID   18991383.
9. Gualtierotti, Jean-Baptiste; Pasche, Delphine; Wang, Qian; Zhu, Jieping (2014). "Phosphoric Acid Catalyzed Desymmetrization of Bicyclic Bislactones Bearing an All-Carbon Stereogenic Center: Total Syntheses of (−)-Rhazinilam and (−)-Leucomidine B" . Angewandte Chemie International Edition. 53 (37): 9926–9930. doi:10.1002/anie.201405842. ISSN   1521-3773. PMID   25048385.
10. Nakamura, Masayuki; Niiyama, Kenji; Yamakawa, Takeru (2009-11-25). "Versatile method for the synthesis of 4-substituted 6-methyl-3-oxabicyclo[3.3.1]non-6-ene-1-methanol derivatives: Prins-type cyclization reaction catalyzed by hafnium triflate" . Tetrahedron Letters. 50 (47): 6462–6465. doi:10.1016/j.tetlet.2009.08.120. ISSN   0040-4039.