Diastereoisomerically pure dinucleosidylphosphorofluoridites and their application in stereospecific synthesis of dinucleosidylphosphorofluoridothionates

Model synthesis of 2,3:5,6-di-O-isopropylidene- S-α-D-mannofuranosyl-N,N-diisopropylphosphoramidofluoridothioate and 2,3:5,6-di-O-isopropylidene-Se-α-D-mannofuranosyl-N,N-di-isopropylphosphoramidofluoridoselenoate via P(III)-OAr intermediates and a thiono-thiolo (selenono-selenolo) rearrangement

“…It has been earlier established that an aryloxy group can readily be replaced by a fluoride anion. 8 Indeed, the fluorophosphoroamidite 4 was formed in almost quantitative yield when 3 was kept for 10 min. with tetrabutylammonium fluoride (TBAF) in acetonitrile solution.…”

New Anions of Pentacoordinate Phosphorus Containing Fluorine and Trifluoromethyl Groups

“…Tetracoordinate triphenylphosphate is converted into the highly fluorinated pentacoordinate phosphorus derivatives 1 or 7 in the reaction with Me 3 SiCF 3 and sources of fluoride. We assume that the nucleophilic substitution at the tetrahedral phosphorus atom follows the addition-elimination process [5] and, as far as F -is in excess relative to the second nucleophile "CF 3 -", the first step of the reaction is the addition of F -to the P=O bond of triphenylphosphate to give intermediate D (Scheme 8) followed by spontaneous PhO -elimination to give (PhO) 2 P(O)F. [10] The ease of adding fluoride to tris(pentafluoroethyl)phosphane oxide [17] and phosphoryl trifluoride [8] further supports this assumption. Upon the substitution of the next PhO group, the highly reactive "CF 3 -" nucleophile can compete with the fluoride anion, as is shown in the proposed reaction mechanism (Scheme 8).…”

Acetyl Fluoride

“…29 This approach led to higher chemical yields than those obtained by acylation of lithium enolates with anhydrides or acyl chlorides. OTMS + RCOF TBAF (2 mol %) THF, 0 °C OCOR R = Me, 82% R = Et, 77% R = Ph, 85% (18) More complex silyl enol ethers can also be acylated by using the same reaction conditions (i. e., TBAF, THF, 0 • C). In the following example, acetyl fluoride and benzoyl fluoride were used in the preparation of 1,3-dioxy-1,3-dienes, which can be further used to access the long-chain polyketide fragments 30 Chemoselective O-benzoylation of the silyl enol ether or lithium enolate derived from acetophenone can be achieved by using benzoyl fluoride and a catalytic amount of TBAF at room temperature in THF (eq 20).…”