Deprotonation reactions of N‐benzyl‐ and N‐allylimines 1 and 4 led to benzo‐annulated 2‐azaheptatrienyl‐ and 4‐azanonatetraenyllithium compounds, which underwent 1,7‐electrocyclization reactions to yield the novel 2,3‐dihydro‐1H‐benzo[c]azepines 3, 5, 11 and 13 or the (5,6‐dihydrobenzocycloocten‐5‐yl)amines 6 after subsequent addition of acyl chlorides, carbamoyl chlorides, imidoyl chlorides or pivaldehyde, respectively. Acyl and carbamoyl chlorides reacted as electrophiles at the nitrogen atom, whereas imidoyl halides and pivaldehyde attacked position C‐5 in the seven‐membered ring. In the case of pivaldehyde, the final tricyclic product 13 is the result of a subsequent nucleophilic attack at the imine moiety after a proton shift. The temperature dependence of the reaction cascades was studied, allowing preferred formation either of the seven‐membered heterocyclic systems 3 and 5 or of the eight‐membered carbocycles 6. All compounds were fully characterized, including by X‐ray diffraction studies of 6c, 6f, 11a and 13a. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Multi-membered N-heterocycles R 0690 1,7-Electrocyclization Reactions of 2-Aza-4,5-benzoheptatrienyl-and 4-Aza-6,7-benzononatetraenyllithium Compounds: Synthesis of Novel 2-Benzazepines and (Benzocyclooctenyl)amines. -Various 2-benzazepines are obtained in moderate to good yield starting from benzylic aldimines (I). N-Allylimines (VIII) give access to either seven-membered heterocycles or through a second deprotonation and an additional 2,3-aza-Wittig rearrangement, eight-membered carbocycles depending on the temperature of the electrophilic reaction. -(SAJITZ, M.; FROEHLICH, R.; WUERTHWEIN*, E.-U.; Eur.

The combination of titanium-catalyzed anti-Markovnikov hydroamination of terminal alkynes with the Strecker reaction is used in the synthesis of unsymmetrical vicinal diamines via the one-pot synthesis of a-cyanoamines. This methodology is further applied to the efficient synthesis of imidazolidinones. An easy-touse bis(amidate)titanium precatalyst permits efficient approaches to heterocyclic chemistry from terminal alkynes.

Deprotonation of 2-alkenylbenzaldehyde N-benzylimines by lithium diisopropylamide and subsequent addition of pivaloyl chloride or methyl chloroformate yields 2-acylated 2,3-dihydro-1H-benzo [c]azepines. This reaction is interpreted as a cascade involving a 1,7-electrocyclization reaction and a subsequent 1,5-hydrogen shift. In contrast, 2-prop-1-enylbenzaldehyde N-allylimine leads to an N-acylated (5,6-dihydrobenzocycloocten-5-yl)amine upon deprotonation and addition of pivaloyl chloride. This transformation is interpreted as a reaction sequence consisting of a 1,7-electrocyclization, the addition of the electrophile, another deprotonation and a [2,3]-aza-Wittig rearrangement, which proceeds in two steps according to quantum chemical calculations.Electrocyclization reactions are important methods for the synthesis of carbo-and heterocycles. Due to their enhanced reactivity 1,n-dipoles and positively or negatively charged unsaturated systems are especially useful for such ring-forming reactions. Often they react in a pericyclic mode with predictable stereochemistry as based on the principle of the preservation of orbital symmetry. 1 The use of such reactions for the formation of heterocyclic benzannulated seven-membered ring systems is of special interest as such substances are otherwise not easily accessible and have found many applications in medicinal chemistry. [2][3][4] Recently we published a new one-step route for the preparation of 4,5-dihydro-3H-benzo[c]azepines (2-benzazepines) 5 by 1,7-electrocyclization of 2-aza-4,5-benzoheptatrienyllithium compounds 2, 5 which were prepared in situ by deprotonation of imines 1. After electrocyclization, the cyclic intermediates 3 were trapped using the electrophiles R 2 X 4. For this work, we adapted an earlier route from our laboratory for the synthesis of 2,3-and 4,5-dihydroazepines (Scheme 1). 6,7 Attractive features of this route are the high diastereoselectivities of the ring-closure reaction (trans-selective for the (E)-styrene derivative) and of the addition of the electrophile R 2 X (trans with respect to R 1 ). In this earlier work, only alkyl halides 4 were used as electrophiles R 2 X.We have now extended our studies on anionic electrocyclization reactions to such experiments in which acyl chlorides, instead of alkyl halides, are used as electrophiles. Interestingly, the use of acyl chlorides as electrophiles in these reactions results in the formation of very different reaction products, as we will show in this report.As previously reported, the lithiated intermediates were prepared by deprotonation of the benzylic aldimine compound 1a-c using lithium diisopropylamide in tetrahydrofuran at -78°C. To achieve cyclization, the reaction mixture was allowed to warm to 0°C, it was then treated with 2.0 equivalents of the acyl halide 6a,b. After warming the reaction mixture to room temperature and aqueous workup, the products were purified by column chromatography. All spectroscopic and analytical data, especially several X-ray structures (Figure 1), are in accord...

Amines Q 0120The Direct Synthesis of Unsymmetrical Vicinal Diamines from Terminal Alkynes: A Tandem Sequential Approach for the Synthesis of Imidazolidinones. -The titanium catalyst for the tandem C-N and C-C bond-forming reaction sequence allows the synthesis of Strecker-type aminonitriles (IV). They are converted to diamines which are isolated as oxalates and used in the preparation of imidazolidinones. -(LEE, A. V.; SAJITZ, M.; SCHAFER*, L. L.; Synthesis 2009, 1, 97-104; Dep. Chem., Univ. British Columbia, Vancouver, B. C. V6T 1Z1, Can.; Eng.) -Mais 20-055