Tfa

Nitroethenyl)indoles can be prepared by reaction of an indole with 2-(dimethylamino)-l-nitroethene in TFA[10]. 3-(2-Nitroethenyl)indolcs can... 

To a stirred ice-cooled solution of 2-(dimethylamino)-l-nitroethene (1.67 g, 14.4mmol) in TFA (7.2ml) was added 6-benzyloxy-l-methylindole (3.42g, 14.4 mmol). The solution was allowed to warm to room temperature and poured into ice water. The product was extracted using EtOAc to give 6-benzyloxy-l-methyl-3-(2-nitroethenyl)indoIe (4.2 g, 95%). 

A traditional method for such reductions involves the use of a reducing metal such as zinc or tin in acidic solution. Examples are the procedures for preparing l,2,3,4-tetrahydrocarbazole[l] or ethyl 2,3-dihydroindole-2-carbox-ylate[2] (Entry 3, Table 15.1), Reduction can also be carried out with acid-stable hydride donors such as acetoxyborane[4] or NaBHjCN in TFA[5] or HOAc[6]. Borane is an effective reductant of the indole ring when it can complex with a dialkylamino substituent in such a way that it can be delivered intramolecularly[7]. Both NaBH -HOAc and NaBHjCN-HOAc can lead to N-ethylation as well as reduction[8]. This reaction can be prevented by the use of NaBHjCN with temperature control. At 20"C only reduction occurs, but if the temperature is raised to 50°C N-ethylation occurs[9]. Silanes cun also be used as hydride donors under acidic conditions[10]. Even indoles with EW substituents, such as ethyl indole-2-carboxylate, can be reduced[ll,l2]. 

Indol-3-ylcarbinols can also be reduced using Et3SiH-TFA. Aryl indolyl-3-ylcarbinols can be formed in situ from 2-alkylindoles and benzaldehydes. These reactions, when run in tandem, provide a versatile route to 3-benzylin-doles[l 1]. Indole itself undergoes reduction to indoline under these conditions. lndol-3-ylcarbinols can also be generated by organomelallic additions to 3-acylindoles[12]. 

NaBFI pellets (10-12 eq.) were added to TFA (25 ml) over 30 min. Hthyl 4-[I-(phcnylsulfonyl)indol-3-yl]-4-oxobutanoate (1.5 mmol) was then added as... 

Hoses, and seals Hospitals Hostaflon Hostaflon ET Hostaflon TFA Hostapur Hostarex DK16 Hostatec... 

Diamide Chiral Separations. The first chiral stationary phase for gas chromatography was reported by GH-Av and co-workers in 1966 (113) and was based on A/-trifluoroacetyl (A/-TFA) L-isoleucine lauryl ester coated on an inert packing material. It was used to resolve the tritiuoroacetylated derivatives of amino acids. Related chiral selectors used by other workers included -dodecanoyl-L-valine-/-butylamide and... 

Proton chemical shift spectra over the range of 0—15 ppm ( 0.1 ppm) TFA, ttifuoroacetic acid DMSO, dimethyl sulfoxide. When complex spectra caused by second-order effects or overlapping resonances were encountered, the range was record (11,12). 

Fig. 26. Representative biomimetic cyclization where P = a protecting group, TFA = trifluoroacetic acid, and (240) (C2H5)3SiCH2C H P(OC2H5)2...

Fig. 5. Synthesis of monophosphatams where Boc is /-butoxycarbonyl R is either CH or OCH and TFA is trifluoroacetic acid.

Fig. 7. Synthesis of monocarbams where P is an amino protecting group and CSI is chlorosulfonyl isocyanate. TFA is trifluoroacetic acid...

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