Olefin difluoro

Strongly polarized l,l-difluoro-2-triphenylsilyloxy-l,3-butadiene (4) reacted with cap-todative olefins 5a and 5b to give [2 + 2] cycloadducts 6a and 6b, respectively (equation 2)3. 

From the study of a microbially mediated oxidation of arteether 28b, sufficient quantities of 7a-hydroxy 180 and 15-hydroxy derivatives 182 were obtained to employ them as intermediates for the preparation of fluorinated compounds. The hydroxyl groups were oxidized to the corresponding aldehyde 187, or ketone 188, with catalytic quantities of tetra- -propylammonium perruthenate (TPAP) in the presence of excess iV-methylmorpholine A -oxide. On reaction with DAST, 187 and 188 were converted into the corresponding geminal difluoro derivatives, 189 (63%) and 190 (42%). In addition to 190, a monofluoro olefin 191 was obtained in 25% yield from 188 on reaction with DAST <1995JME4120>. 

Anesthesia is achieved rapidly and smoothly with sevoflurane, and recovery is more rapid than with isoflurane. However, sevoflurane is chemically unstable when exposed to carbon dioxide absorbents in anesthesia machines, degrading to an olefinic compound (fluoromethyl-2,2-difluoro-l-[trifluoromethyl]vinyl ether, also known as compound A) that is potentially nephrotoxic. In addition, sevoflurane is metabolized by the liver to release fluoride ions, raising concerns about potential renal damage. 

Difluorocyclopropanes and Difluoro-olefins New Compounds with Acaricidal and Insecticidal Properties ... 

In the case of the fluorinated ethylenes, it is known through work of Bartlett and his collaborators that the reaction is stepwise by way of a biradical intermediate.17 Much of the evidence supporting this conclusion has been obtained from the study of additions of l,l-difluoro-2,2-dichloroethylene, abbreviated 1122, to dienes. Scheme 1 outlines six possible general routes, each of which has several potential stereochemical variations, that addition of an olefin to a diene could follow. When 1122 reacts with butadiene and simple substituted butadienes, the products are entirely cyclobutanes consequently, we may restrict attention... 

The attack at the CFZ group of l,l-dichloro-2,2-difluoroethylene by EtMgBr (Tarrant and Warner, 1954), the attack at the CF2 group of phenoxytrifluoroethylene by phenoxide ion (England et al., 1960) and the replacement of the 1-fluorine of 1-diethylaminotrifluoroethylene with water (Yakubovich et al., 1966) are in line with predictions based on the carbanionic theory. On the other hand, the attack of triethyl phosphite at the terminal difluoro group of w-iodoperfluoro-1-olefins (Knunyants and Pervova, 1962) could be explained by steric control. 

An intramolecular reductive addition of a,a-difluoro acetal radicals to olefins in a 5-exo-trig mode has been reported [95TL3531]. The reaction with the corresponding a-bromo-a,a-difluoroacetates gave no cyclized products. This method provides ready access to a,a-difluoro-y-lactones 34 in good yields. 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1,1-difluoro olefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a l,3-dichloro-2-propanol derivative and ethyl-... 

In this case, however, 1-isopropyl-4,4-difluoro-2-hexafluoroethyl-3-tri-fluoromethyl-li/-azetine is formed, which points to a direct reaction of olefin 1 with isopropylamine. This suggests that steric factors play a definite role in this reaction. Indeed, the interaction between olefin 1 and ethylamine is the second route of this reaction. If, however, no isomerization of perfluorolefin takes place under the action of the starting alkylamine, or if a symmetrically substituted structure is formed, then only one heterocyclic compound is obtained. This is realized for perfluoro-5-azanon-4-ene. Irrespective of the character of the nucleophilic reagent, diazete derivative 20 is produced. 

Elimination of the fluoride ion from the CF3 group of carbanion B leads to the formation of olefin 54 with a terminal multiple bond. Intramolecular cyclization of olefin 54 gives a minor amount (5%) of seven-membered heterocycles 5-pentafluoroethyl-6-trifluoromethyl-5,7-difluoro-l,4-dioxacy-cloheptene-6 52 and 5-pentafhioroethyl-6-trifluoromethyl-7,7-difluoro-l,4-dioxacycloheptene-5 53. 

With CF3C=CCF3 or olefins with an internal double bond such as cis- or fraras-F-2-pentene, F-cyclobutene, or l,2-dichloro-l,2-difluoro-ethylene, or with a geminally disubstituted olefin such as 1,1-dichloro-2,2-difluoroethylene, only fully fluorinated products were obtained, likely through a nucleophilic fluorination mechanism. This fact, plus the necessity for a Lewis acid catalyst for addition to proceed, is evidence for an electrophilic addition mechanism. Others have suggested polar addition of BF3 to the olefin with RfBF2 as a reactive intermediate (294). 

Grubbs and coworkers used (4a) to perform olefin metathesis with 1,1-difluoroethelyene a metathesis partner that had theretofore been unavailable for reaction consideration. While metathesis did occur, the difluoro carbene Ruthenium complex (4m) (Figure 2) was not an effective catalyst itself thus, little if any turnover was observed, although this did provide a potential convenient pathway for constructing dihalocarbene-metal complexes. 

A facile synthesis of fluoro-olefins through Pd(0)-catalyzed reductive defluorination of allylic g m-difluorides, in particular y,y-difluoro-a,P-enoates was recently reported (see Scheme 10.16) [26]. Stereoselectivities were moderate to high (.E Z= 1 1-1 9). 

Similarly, the reaction of diethyl 1-formyletliylphosphonate witli diethyl 1-methoxy-l-(meth-oxycarbonyl)methylphosphonate in the presence of NaHMDS in THF at room temperature affords the expected Y-methoxy-P,Y-unsaturated phosphonate in 39% yield. Diethyl 1,1-difluoro-l-formylmethylphosphonate hydrate undergoes an olefination reaction with stabilized methylphosphonate carbanions under a variety of conditions to give 3-substituted diethyl l,l-difluoro-2-propenylphosphonates in 45-78% yields. ... 

Scheme 2.191 Synthesis of fluoro and difluoro olefins by metathesis of carbonyl compounds with fluoroalkyl phosphoranes (SBAH = sodium bis(methoxyethoxy)aluminum hydride) [12d].

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