Imines, from azides

Benzodiazepin-2-ones are converted efficiently into the 3-amino derivatives by reaction with triisopropylbenzenesulfonyl (trisyl) azide followed by reduction <96TL6685>. Imines from these amines undergo thermal or lithium catalysed cycloaddition to dipolarophiles to yield 3-spiro-pyrrolidine derivatives <96T13455>. Thus, treatment of the imine 50 (R = naphthyl) with LiBr/DBU in the presence of methyl acrylate affords 51 in high yield. 

Several heteroaromatic azides react with isoprene addition occurs as expected at the less hindered double bond, and satisfactory yields of triazolines are obtained after several days of reflux (Scheme 31).183 Azidoazolopyri-dazines, however, yield only the imines from styrene and 2-vinylpyridine.91... 

Triazolines formed from azides attached to electron-withdrawing groups are much less stable and the decomposition products are obtained directly. A -Picryl imines were obtained in the reaction of picryl azide with a series of olefins yields were 70% with cyclopen-tene, 58% with cycloheptene and only 20% with cyclohexene. No imine was formed with norbomene . 

Lithium aminoborohydrides are obtained by the reaction of -BuLi with amine-boranes [FF2, FH5, NT2]. They can be generated in situ as THF solutions or as solids when formed in diethylether or hexane (n-BuLi must then be used in sub-stoichiometric amounts). They are stable under dry air and are slowly decomposed by water [NT2] or methanol so that workup of the reactions mixtures can be carried out with 3M HCl. They reduce alkyl halides (Section 2.1), epoxides (Section 2.3), aldehydes, and ketones (Section 3.2.1) (in the latter case with an interesting stereoselectivity [HFl]), and esters to primary alcohols (Section 3.2.5). a,(3-Unsaturated aldehydes, ketones, and esters are reduced to allyl alcohols (Section 3.2.9) [FF2, FS2]. Depending on the bulkiness of the amines associated with the reagent and to the substrate, tertiary amides give amines or alcohols (Section 3.2.8) [FFl, FF2]. Amines are also formed from imines (Section 3.3.1) [FB1 ] and from azides (Section 5.2) [AFl]. However, carboxylic acids remain untouched. 

Alkyl-1,2,4-triazole 4-imines can be also prepared from azides and 1-alkyl-1,2,4-triazoles.87 For instance, the IV-imine 53 is produced when acetyl azide, which under these conditions gives acetyl nitrene,89 is irradiated in the presence of 1-benzyl-s-triazole. 

Phenyl azide appears as a rather unreactive 1,3-dipole. Of the azomethine imines that follow, sydnone is more stable than the open cyano-derivative. Diazomethane is a very reactive compound, but double phenyl substitution reduces its reactivity. The highest rate coefficients are those of reactions of the mesoionic oxazolone. Reactivity varies by five or six orders of magnitude from azide to mesoionic oxazolone. 

Imidazolium salts, catalysts of the benzoin condensation 723 deuterium exchange in 705 Imines, from an azide and ethylene 725, 726 reduction of 68... 

Raasch, and Schaumann and co-workers, have studied the reactions of bis (trifluoromethyl)thioketene (83 R1 = CF3) with alkenes, with thioketones, and with carbodiimides or Schiff-base imines. The products were, respectively, thietans, 1,3-dithietans (84 R1 = CF3), and 1,3-thiazetidines (85 R1 = CF3) (from the carbodiimide).114,115 With phenyl azide the 1,2,3,4-thiatriazoline (86 R = CF3) is formed subsequent pyrolysis yields2,l-benzisothiazole.114... 

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