Dialkyl ethers poly complexes

Stable dialkyl ether poly(hydrogen fluoride) complexes (R20-[HF]n, R = Me, Et, n-Pr) have recently been developed by Prakash, Olah, and colleagues.33 DFT calculations suggest a cyclic poly(hydrogen fluoride) bridged structure. Dimethyl ether-5 HF (DMEPHF) was shown to be a convenient and effective fluorinating agent (see Section 5.10.1). 

Stable dialkyl ether poly(hydrogen fluoride) complexes have been shown to be convenient and effective fluorinating agents.553 Various open-chain and cyclic alkenes undergo hydrofluorination with dimethyl ether-5 HF (DMEPHF) atroom temperature to furnish the corresponding fluoro derivatives in high yields (73-94%) with excellent selectivities. The fluorination of secondary and tertiary alcohols exhibit similar features. Bromofluorination of alkenes can also carried out with DMEPHF in combination with /V-bromosuccinimide. The homologous diethyl ether and dipropyl ether complexes are also suitable for fluorinations. 

Bucsi 1, Marco Al, Olah GA, Prakash GKS, Rasul G, TdtokB. 2002. Stable dialkyl ether/ poly(hydrogen fluoride) complexes dimethyl ether/poly(hydrogen fluoride), a new, convenient, and effective fluorinating agent. J Am Chem Soc 724 7728-7736. 

Catalytic asymmetric intramolecular hydrosilylation of dialkyl- and diarylsilyl ethers of bis(2-propenyl)methanol (245) catalyzed by (R, R)-DIOP-Rh or (R)-binap-Rh complex, followed by Tamao oxidation, gives (2S, 3R)-2-methyl-4-pentene-l,3-diol (247) with 71-93% ee and excellent syn selectivity (syn/anti = 95/5- > 99/1) (equation 96)249. The enantioselectivity of this reaction depends on the bulkiness of the silyl moiety, i.e. the bulkier the substituent, the higher is the enantiopurity of the product, except for the case of 2-MeCgH4 R = Me, 80% ee (binap-Rh) R = Ph, 83% ee (DIOP-Rh) R = 2-McC.fiI I4, 4% ee (DIOP-Rh) R = 3-MeC6H4, 87% ee (DIOP-Rh) R = 3,5-Me2C6H3, 93% ee (DIOP-Rh). This methodology is successfully applied to the asymmetric synthesis of versatile poly oxygenated synthetic intermediate 249 (equation 97)249. 

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