Nitrile oxides

Stereoselective Synthesis of Masked Amino‐polyols via Osmylation of 4,5‐Dihydro‐5‐vinylisoxazoles

“…A stereospecific reaction was observed in a case with less flexibility. Thus, cycloaddition of acetonitrile oxide [9] to cyclopentadiene [8] gave dihydroisoxazole 19, in which the double bond is specifically attacked from the less hindered side to give one diastereoisomer 20 as the product of the 'until-attack, As mentioned in the introduction and as pointed out by several authors, compounds of the type of 10-18 and 20 represent useful synthons for aminosugars [l] [5] [18], since reduction of the dihydroisoxazole ring produces y -amino alcohols with high degrees of stereoselectivity [3] [6]. Therefore, we briefly investigated the osmylation of some selected derivatives of 1-9.…”

“…for C,H,,NO (139.20): C 69.03, H 9.41, N 10.06; found: C 69.10, H 9.45, N 10.10. (8). Yield 43 YO, purified by flash chromatography (Et20/hexane 3 :7).…”

“…A sulfoxide-mediated approach to enantiomerically pure compounds is also described.Results and Discussion. -Trapping of nitrile oxides [8], generated in situ from nitroethane [9] or from the appropriate hydroximoyl chloride [lo], with a variety of commercially available dienes [ 111 gave 4,5-dihydroisoxazoles 1-9 in high yields. The cycloaddition proceeded, as expected [8] [lo], regioselectively') on the less substituted and/or less hindered double bond of the dienes via a stereospecific cis-attack.…”

Thermal Transformation of Arylamidoximes in the Presence of Phosphorus Ylides. Unexpected Formation of 3‐Aryl‐5‐arylamino‐1,2,4‐oxadiazoles.

“…Interestingly, diaryloxadiazoles 9 were also formed upon heating at controlled temperatures in the absence of acetic acid showing that the presence of a carboxylic acid was not critical for the above transformation. Concerning the latest steps of the mechanism for the formation of bis-aryloxadiazoles three possibilities were suggested: i) reaction [7] between arylnitrile and arylnitrile oxide originally formed from 2, ii) reaction [8] of nitrile oxide formed with starting amidoxime, iii) reaction [9] between the nitrile formed and the starting amidoxime. The last mechanism is supported by the fact that diarylfuroxans, always formed by further dimerization of nitrile oxides [10], has not been isolated in the reactions studied.…”

The reactions of 2,4‐dichlorobenzonitrile oxide with enolizable schiff bases

“…Ether 0-ketoimines or cyanoacetic esters (5). Morocchi, et al, however, found that the reaction of benzonitrile oxide with acetophenone or propiophenone imines furnished a single product, the 4,5-dihydro-l,2,4-oxadiazoles (6).…”