The Stereochemistry of Organometallic Compounds. XLIII. Rhodium-Catalysed Reactions of 2-(Alkenyloxy)benzylamines and 2-(N-Allyl-N-benzylamino)benzylamine

Reactions of 2-( allyloxy ) benzylamines with H2/CO in the presence of rhodium catalysts give 1,3-benzoxazines, and 2-(N- allyl-N-benzylamino ) benzylamine gives a quinazoline . These reactions have been shown to involve allylic cleavage followed by regioselective carbonylation at the internal carbon atom as demonstrated by crossover experiments. Reactions of longer chain ( alkenyloxy ) benzylamines under similar conditions give polymeric material.

Elf stabile C5H9+-Kationen in der Gasphase. Zur dissoziativen Ionisierung von 31 isomeren C6H9Br-Verbindungen / Eleven Stable C5H9+ Cations in the Gas Phase. On the Dissociative Ionization of 31 Isomeric C5H9Br Compounds

Collisional activation mass spectrometry (CA) reveals the existence of 11 stable C5H9+ cations in the gas phase, e. g. the substituted allyl cations a, b, c, d,and e, the sub-stituted vinyl cations f, g, h, and i, the methyl cyclobutyl cation j and the cyclopentyl cation k, respectively. The ethyl substituted allyl cation a is formed via dissociative ionization of the isomeric precursors 1, 3, 4, 5, 18, 19, 20, 22, and 28 by means of various mechanistic processes, whereas the 1,3-dimethylallyl cation b is generated from both 2 (by allylic cleavage) and in part from the stereoisomeric cyclopropan derivatives 25, 26 and 27. 6+ -gives a mixture of the vinyl cations 1 and g. From 13 and 14 the main product generated is the 1,2-dimethylallyl cation d, which is formed directly from 11 and also by quite complicated processes from 13, 14 and to a certain extent from 25, 26 and 27. The dissociative ionization of 9, 15, 16, 21, 24 and (in part) 23 give rise to the formation of the substituted vinyl cation h. Decomposition of 23+ • results not only in formation of h but generates also the 1,1-dimethylallyl cation e. From 29+-and 30+-both the methylcyclo-butyl cation j and cyclopentyl cation k are produced, whereas the isomeric precursor 28 gives mainly the substituted allyl cation a and a second, as yet, unidentified C5H9 cation. In general, it can be stated that the gas phase chemistry of cation radicals of substituted cyclopropanes is characterised by multistep-reactions, commencing with spontaneous ring opening. The so formed intermediates undergo various rearrangements (including hydrogen and alkyl shifts) prior to expulsion of Br·. Direct elimination of Br· from intact cyclopropan-like structures, followed by ring opening of the intermediate cyclopropyl cation, cannot compete with the above-mentioned multistep-sequences.

Acylation du (cyclopropylméthyl)triméthylsilane. Une nouvelle voie d'accès aux énones non conjuguées

Acylation of (cyclopropylmethyl)trimethylsilane using RCOCl/AlCl3 (R: saturated hydrocarbon group) constitutes a mild, convenient route to β,γ-unsaturated ketones free from the conjugated isomers. With α,β-unsaturated acyl chlorides a competitive reaction between the C—H and C—Si allylic cleavage is observed whereas chloroacetyl chloride affords the γ,δ-ethylenic corresponding ketone. A mechanism involving the catalytic role of HCl in the formation of β,γ-unsaturated and chloroketones is proposed.