Imines diimide

Other imine-like adduct structures reported include the phosphinimine of Entry 30149 and the coordinated nitrile in the vanadocene complex shown in Entry 31.150 The tellurium diimide dimer (Entry 32) also coordinates one equivalent of B(C6F5)3 and this adduct has been crystallographically characterized.151 The structure features weak... 

Such processes may be operative in imines and their derivatives (oximes...) azo compounds, diimides etc. 

The most obvious disconnection depends on which Kckule form of the pyridazine you happen to draw. Disconnection of both C-N bonds reveals either 175 an encouraging 1,4-diketone 176 and a most discouraging molecule of diimide 177 or, by imine disconnection, 178 an encouraging molecule of available hydrazine and a rather discouraging Z-enedione 179. 

The addition of N-phenylbenzophenone imine yields only the 4-l-2 adduct at first, but this can be thermally dissociated and eventually converted into the more stable 2-1-2 isomer244. Acetone ketazine also forms a 2-1-2 cycloadduct with 54244. No 2 + 4 adduct formation was observed. Bis(trimethylsilyl)diimide reacts with 54 to yield the 2 + 2 cycloadduct, a siladiazetidine which decomposes upon warming to 50 °C (equation 127)243. Azobenzene and PhN=NSiMe3 behave similarly244. 

These A-sulfinyl Diels-Alder reactions are also highly stereoselective, giving products of syn addition to the 1,3-diene. The same holds true for the sulfur diimide cycloadditions . The stereoselectivity with respect to the dienophile is not very well known because the stereochemistry of sulfur in the starting A-sulfinyl dienophile and in the resulting thiazine derivatives has usually not been determined. A representative sample of the stereoselective preparation of 3,6-dihydrothiazine 1-oxides and 1-imines is shown in Scheme 34 <84JA786i, 84JA7867>. 

The adducts formed in these cases are the analogous dihydrothiazine imines 2. Symmetrical and unsymmetrical sulfur diimides are available, and both can act as heterodienophiles. In adducts 1 and 2 the sulfur center is chiral, and the implications of this fact will be discussed in some of the following sections. 

The cycloadducts of sulfur diimides exhibit hydrolytic behavior very similar to that of dihydrothiazine oxides (Scheme 1-XI). Alkaline hydrolysis of a dihydrothiazine imine affords an intermediate sulfinamide which, on treatment with aqueous acid, yields a homoallylic amine, presumably via a retro-ene process. A homoallylic amine is formed directly from a cycloadduct on acidic hydrolysis. ... 

The methods for generating acyl ketenes (Scheme 7-V) and their subsequent in situ participation in [4 + 2] cycloadditions with a wide range of hetero- or olefinic and acetylenic dienophiles (Scheme 7-VI), including acyl ketenes,185 186,197 carbonyl compounds, 86-188 nitriles,1874,189,191 isocyanates and isothiocyanates,1864,190,191 ketenes,191 imines,1864,1874,191,192 carbo-diimides,l87c 190,191,193 ynamines,194 ketene acetals,1864,195 enol ethers,1864,191,196 and V-sulfinylamines197 have been extensively reviewed.5,9,12 Two reports have detailed the 4-n- participation of allenic ketones in [4 + 2] cycloaddition reactions [Eq. (51)].198,199... 

A detailed mechanistic study of the chemical and electrochemical oxidative dehydrogenation of the iron(II) complex 14 has been reported. The key intermediate is an iron(II) amido complex which is tautomeric with an iron(II) amido radical species it is this species which undergoes electron loss to give the iron(II) complex of a C-protonated imine (Scheme 6). The reaction of dicyclohexylcar-bodiimide, RN=C=NR, with ReClg results in nucleophilic attack of halide upon the diimide to yield complexes of RNHCC1=NR. The complex... 

One specialized and readily available carbodiimide, called dicyclohexyl-carbodiimide (usually abbreviated DCC), will be used to illustrate this transformation it has structure 78. Use of this reagent to form esters led to the discovery that adding a catalytic amount of an amine base gives higher yields. This observation will be used, but will not be explained further in this discussion. When 3-methylbutanoic acid (77 isobutyric acid) is stirred with tert-butanol in the presence of a catalytic amount of 4-pyrrolidinopyridine (79), for example, er -butyl 3-methylbutanoate (80) is isolated in 65% yield. In addition to the ester, one molar equivalent of dicyclohexyl urea (see 87) is also isolated. The mechanism that explains these results begins by noting that the diimide carbon in 78 is like a double imine and bond polarization makes the central carbon atom very electrophilic. 

Although neither the use of triphosgene nor of oxalyl chloride afforded the desired amido chlorides, the thiazetidinone has been found [561] to be a highly versatile intermediate allowing the facile conversion of thioureas into either carbo-diimides or isoureas in good yields. 3-(4-Fluorophenyl)-l,3-thiazetidin-4-one-2-(4-fluorophenyl)imine 770 was obtained in 63% yield as the main product from the reaction of N,N -bis(4-fluorophenyl)thiourea 769 with one-third of an equivalent of triphosgene. 

When using aliphatic aldehydes tethered to arene motifs as substrates, an enan-tioselective sequential aza-hetero-Diels-Alder and Friedel-Crafts reaction was successfully achieved by the same group [63]. Similarly, optically active lactone[3,3-b] piperidine skeletons 140 can be obtained by tandem aza-hetero-Diels-Alder reaction-hemiacetal formation-oxidation from a,P-unsaturated imines 136 and glutaraldehyde (139) (Scheme 38.41) [64]. Enamine catalysis of the inverse-electron-demand aza-hetero-Diels-Alder reaction was further extended to o-benzoquinone diimide 141 by Chen s group [65]. Various hydroquinoxalinones 142 can be obtained in high yields with excellent enantioselectivities (Scheme 38.42). 

The installation of the pharmacologically important isoquinoline group was achieved by a Stille coupling. Reduction by diimide yielded the trans-fused perhydroindane subunit in 329. An oxidation, enol triflation and reduction sequence converted 329 to enone 331. Enol triflation and deprotection afforded 332. Palladium-catalyzed vinylation, followed by a Parikh-Doering oxidation gave 333. The final and rather splendid step consisted of dimethyl imine-formation and vinysilane cyclization to furnish cortistatin J in high yield and with the correct dimethylamine stereochemistry (Scheme 18.66). 

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