Selectfluor (F-TEDA-BF₄) C₇H₁₄B₂ClF₉N₂

Biographical Sketches

Laxmi Manral was born in 1981. She received her B.Sc. in 2002 from Delhi University and M.Sc. in Organic Chemistry in 2004 from Kumaun University, Nanital, India. She joined DRDE in 2005 as a JRF and currently pursuing her Ph.D. under the tutelage of Dr. R. C. Malhotra, Joint Director of DRDE. Her present research is focused on narcotic analgesics; synthesis and stability studies.

Introduction

Selectfluor [1] is one of the most reactive electrophilic ­fluorinating reagents. It is a white, free-flowing, virtually non-hygroscopic, high-melting solid (mp 170 °C) [2] and is soluble in few polar solvents, e.g. MeCN, DMF, H₂O, MeNO₂, ionic liquids. It is a safe, stable, non-toxic, easy-to-handle reagent that is amenable to industrial production. It provides an alternative to molecular fluorine which is a hazardous, highly toxic, strong oxidant, with little or no specificity. [1] Selectfluor helps in the fluorination of steroidal enol acetates, [3] monofluoro ketomethylene dipeptide isosterase, [4] carbanions, and Grignard reagents, and in the α-fluorination of sulfides, [2] aldehydes and ketones. [5] Besides these properties (in two-electron processes), it also shows oxidative characteristics, and forms potent ­indium sources with molecular iodine, although it decomposes in the presence of iodide ion. It is also useful in the conversion of common anions into electrophiles. [6]

Preparation

Selectfluor is commercially available. It can be prepared by the alkylation of DABCO (TEDA) with dichloro­methane. After counter-anion exchange with NaBF₄ and precipitation of NaCl from MeCN solution, fluorination with F₂ provides F-TEDA-BF₄. [1]

Abstracts

(A) Selectfluor is a versatile reagent for fluoroalkylation of alkenes and acetylenes under mild conditions. This reaction follows ­Markovnikov-type regioselectivity. [7] [8]
(B) Selectfluor also helps in the deprotection of PMP, THP, and 1,3-dithiones. Acetonitrile and nitromethane (5% H2O content) can be used as solvent. In the presence of 1.2 equivalents of Selectfluor, deprotection is complete in five hours. [9]
(C) Selectfluor acts as a mediator for the introduction of a per­fluoroalkyl moiety containing a functional group at the benzylic position in hexamethylbenzene, in the presence of polyfluoroalcohol or potassium salts of perfluoroalkane carboxylic acid. [10]
(D) Selectfluor provides one-pot fluorination and anomeric functionalisation of a carbohydrate. In the presence of a nucleophile, it reacts with glycals to give 2-deoxy-2-fluoro derivatives with concurrent introduction of a nucleophile to the anomeric position. [11]
(E) Selectfluor can be used as an excellent promoter for allylation of aldehydes and amines with allyltributyltin in one step, to form homoallylic alcohols or amines. [12]
(F) Selectfluor allows the green electrophilic fluorination of indole compounds in high chemoselectivity and yield. In the presence of thiols, intermediate sulfides are formed. [13]
(G) Selectfluor provides a straightforward route for the synthesis of difluorinated carbonyl compounds upon reaction with enamines under mild conditions. [14]

References

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2 Lal GS. J. Org. Chem.  1993,  58:  2791 

3a Hodson HF. Madge DJ. Widdowson DA. J. Chem. Soc., Perkin Trans. 1  1995,  2965 

3b Banks RE. Mohialdin-Khaffaf SN. Lal GS. Sharif I. Syvret RG. J. Chem. Soc., Chem. Commun.  1992,  595 

4 Hoffmann RV. Tao J. J. Org. Chem.  1996,  64:  126 

5 Enders D. Huttl MRM. Synlett  2005,  991 

6 Syvret RG. Butt KM. Nguyen PT. Bulleck VL. Reith RD. J. Org. Chem.  2002,  67:  4487 

7 Zupan M. Iskra J. Stavber S. J. Org. Chem.  1995,  60:  259 

8 Stavber S. Sotler T. Zupan M. Tetahedron Lett.  1994,  35:  1105 

9 Liu J. Wong C.-H. Tetrahedron Lett.  2002,  43:  4037 

10 Stavber S. Kralj P. Zupan M. Acta Chim. Solv.  2002,  49:  5537;   Chem. Abstr.   2003,  138:  169926k 

11 Burkart MD. Zhang Z. Hung S.-C. Wong C.-H. J. Am. Chem. Soc.  1997,  119:  11743 

12 Liu J. Wong C.-H. Tetrahedron Lett.  2002,  43:  3915 

13 Baudoux J. Salit A.-F. Cahard D. Plaquevent J.-C. Tetrahedron Lett.  2002,  43:  6573 

14 Peng W. Shreeve JM. J. Org. Chem.  2005,  70:  5760