Cyclization substitution

Oxidative cyclization, substituted stil-benes to phenanthrenes, 46, 91 4-Oxo-l, 1-dimethyIpiperidinium salts, 46,82... 

CuCl-catalyzed decomposition of iodonium ylides prepared from /3-keto esters and diacetoxyiodobenzene, has been developed (equation 151)331. 1-Methylbenzvalene is obtained in a good yield by treating a mixture of lithium cyclopentadienide and 1,1-dichloroethane with butyllithium332. The tandem cyclization substitution in l-selenyl-5-hexenyllithiums derived from corresponding selenacetals via selenium/lithium exchange produces bicyclo[3.1.0]hexane derivatives333. 

Iodolactonization of y, o-unsaturated alcohols results in preferential formation of tram-2, 5-disubstituted tetrahydrofuranes. However, the corresponding benzyl ethers cyclize preferentially to the cis-isomers. The alkyl group must be bulky enough to exert a steric effect, but not to prevent cyclization. Substituted benzyl ethers are particularly useful. Examples of this steric control are illustrated for the preparation of tram- and c/s-linalyl oxide (equations I and II).10... 

Hence, N,N-diallyl-(2-chlorophenyl)-amine and N-allyl-N-(2-chlorophenyl)-acetamide react with MesSn and Ph2P ions in liquid ammonia under photostimulation to afford cyclized-substituted compounds in good yield (Scheme 10.51) [67]. 

Dilithiated 1-tetralone oxime, prepared by treatment of 372 with an excess of LDA, was condensed with a variety of esters, affording, by acid cyclization, substituted 4,5-dihydronaphth[l,2-r ]isoxazoles 373 (Scheme 90) <2000SC3391>. 

Reductive cyclizations. Substituted pyrrolidines and piperidines are obtained by the Ti(Il)-mediated cyclization of enyne carbonates. 5-Ketoesters and ketonitriles undergo radical cyclization with CpjTiPh which is obtained as a dark green solution by sequential treatment of Cp TiClj with i-PrMgCl and PhMgBr. 

Cyclizations. Substituted furans are formed from HgClj-catalyzed cyclization of allenyl carbinols which are derived from 3-methoxy-l-phenylthio-l-propyne. ... 

Orth, R.E., and J.W. Jones Cyclized substituted thioureas. I. Preparation... 

Ketyls generated by the reaction of SmE with aldehydes and ketones have been incorporated into numerous sequential processes in which a radical reaction is involved. Sequential radical processes, radical cyclization/carbonyl additions, radical cyclization/substitution reactions, nucleophilic acyl substitution/radical cyclizations, cyclization/elimination processes, and others have all been realized. Because these types of reactions have been extensively reviewed [2b, 25], further details will not be given here. Needless to say, new sequential processes based on SmE-promoted ketyl/olefin coupling reactions are still being developed (Eq. 75) [88]. 

There are also several indole syntheses which are based on the use of arylhydroxyamines and which involve a [3,3]-sigmatropic rearrangement similar to that involved in Fischer cyclization. Substituted JV-acetylarylhydroxyamines can be vinylated by palladium-catalyzed addition-elimination with vinyl acetate. Under mild heating, rearrangement and cyclization occurs (Scheme 61) <84HCA1647, 88HCA344>. 

In 2010, Enders et al. reported on an organocatalytic, one-pot, three-component reductive amination/aza-Michael sequence. They used bis(2,4,6-triisopropyl-phenyl)-l,l -binaphthyl-2,2 -diyl hydrogenphosphate (TRIP) 319 as the organocatalyst and 2-binaphthyl substituted benzathioazole derivatives 320 as the reducing agent and t-BuOH was used as the base. After alkylative cyclization, substituted tetrahydroisoquinoline derivatives 318 were formed in high yields with excellent stereoselectivity (Scheme 40.69). 

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