Trichloroacetamides cyclization

The reduction of the trichloroacetamide derivative 56 with (TMS)3SiH afforded 57 in a 60% yield (Reaction 7.58) [68]. The final product is the result of cyclization and further removal of two chlorine atoms. In fact, 3.5equiv of silane and 1.1 equiv of AIBN are used. 

Demethoxyerythratidinone (10), one of the simplest of the erythrina alkaloids, was isolated in 1973 by Barton et al. from Erythrina lithosperma [14]. A concise approach to such Erythrina alkaloids using a disfavored 5-endo-trig radical cyclization mediated by nickel powder was described by Zard and coworkers [15]. A-Alkenyl trichloroacetamide 7 was... 

Not only trichloroacetate or trichloroacetamide systems can be applied. Weinreb and coworkers reported a few copper-catalyzed 5-exo ATRC of 2,2-dichloro-3-oxo-6-heptenoates using 3.2 mol% CuCI and PPh3 as a ligand [304]. A 1.6 1 mixture of regioisomeric 5-exo and 6-endo products was obtained with low diastereoselectivity. 5-exo Annulations and 6-exo cyclizations gave the products with 1 and 2.7 mol% Cu catalyst in 82-99% and 91% yield, respectively. Ghelfi and colleagues found that dichloroacetaldehyde-derived mixed 0-allylic acetals served... 

The thermal rearrangement of O-allyl trichloroacetimidates 1 affords the corresponding 7V-allyl amides 31 2, which have been cyclized with the aim of obtaining amino diols or amino alcohols different to those from the cyclization of the trichloroacetimidates. Cyclization of these latter substrates 1 leads to 4,5-dihydro-4-(l-iodoalkyl)oxazoles 2, while treatment of unsaturated trichloroacetamides 3 with /V-iodosuccinimide3 in chloroform affords the corresponding 4,5-dihydro-5-(l-iodoalkyl)oxazoles 4 in high yield. These heterocyclic products are protected forms of the corresponding amino alcohols. 

Cyclization of N-trichloroacetamides using copper(I)-bis[(45)-(l-methylethyl)oxazolin-2-yl]methane complex afforded the corresponding y-lactams in high yield (85-95%) but low diastereoselectivity (6%) (eq 10). ... 

In this connection, intramolecular Michael addition of 0-carbamates to a,3-unsaturated esters (Scheme 60)," iodo cyclization of allylic and homoallylic trichloroacetamidates" or aminomercuration of alkenic carbamates" has been used for the preparation of amino alcohols. 

Spiro-indolenines were generated using a halogen atom transfer radical 5-exo cyclization of trichloroacetamides <05CC4827>. 

Highly stereoselective preparation of either trans- or m-/J,y-dia1kyl-y-lactam derivatives is achieved by cyclization of l-methyl-2-propenyl trichloroacetamides. The choice of the nitrogen protecting group controls the steric outcome of the reaction. The mechanistic aspect that determines this stereoselectivity is unclear26. 

A-Alkenyltrichloroacetamides give y-lactams by 5-endo cyclization in competition with 4-exo cyclization as shown in Scheme 2. In the presence of 2 equiv of diphenyl diselenide, trichloroacetamide 11 afforded y5-lactam 14 in 39% yield along... 

Lactams. Trichloroacetamides I are induced to undergo cyclization. doles directly, as benzylic C-Cl bom... 

In a more recent elaboration of this work, a domino radical cyclization was observed when a similarly built trichloroacetamide bearing a tethered alkene on the... 

Reports on three useful transition metal catalysed cyclization routes to nitrogen heterocycles have appeared this year. In an extension of their earlier work on the synthesis of trichlorlnated T-butyrolactams by copper- or ruthenium-catalysed cyclization of -allyl-trichloroacetamides, Itoh and co-workers have now shown that... 

Much more common, however, is the initiation of cyclization of A-allyl trichloroacetamides to y-lactams at low temperature, which often takes place in excellent 3ueld. It has been found that the y-lactam forming process takes place with only 10 mol % of CuCl when acetonitile is used as solvent and TMEDA as ligand. Sequential reactions consisting of the cyclization of N-allyl trichloroacetamide followed by the inter- or intramolecular carbon-carbon bond forming reactions at the a-position of the lactams were also reported eqs 6 and 7). ... 

This researeh was extended to include non-symmetrical amidinate complexes of the same type with mixed Cp and Cp ligands, such as the cationic species [Cp Ru 2-PrN=C(Me)NPr )RuCp(L)] (138 L = none, NCMe, CNBu , PMc3 BF4 salts). For 138 (L = CNBu ), there is NMR evidence that the isonitrile ligand switches between the ruthenium centers. Coordinatively unsaturated intermediates play a key role in catalytic processes, and thus complexes 138 (L = none PFe salt) and 135 (PFe salt) were found to catalyze the atom-transfer radical cyclization of A7-allyl trichloroacetamides. It was discovered that the greater protection offered by the steric bulk of the Cp" ligand led to the superior performance of 135 (PF salt). ... 

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