Ring closure reductive

Alkenyl Fischer carbene complexes can serve as three-carbon components in the [6 + 3]-reactions of vinylchro-mium carbenes and fulvenes (Equations (23)—(25)), providing rapid access to indanone and indene structures.132 This reaction tolerates substitution of the fulvene, but the carbene complex requires extended conjugation to a carbonyl or aromatic ring. This reaction is proposed to be initiated by 1,2-addition of the electron-rich fulvene to the chromium carbene followed by a 1,2-shift of the chromium with simultaneous ring closure. Reductive elimination of the chromium metal and elimination/isomerization gives the products (Scheme 41). 

When a formaldehyde/formic acid mixture was used for cyclization of the cis and trans isomers of 262 (R = H, Me), interesting transformations were observed. In the reactions of methylcarboxamides 262 (R = Me), ring closure and A-methylation took place, resulting in 1,3-dimethyloctahydroquinazolinones 263. Under the same conditions, in the reactions of the unsubstituted amides, ring closure, reductive methylation and hydroxymethylation on the amide nitrogen took place, resulting in the l-methyl-3-hydroxymethyloctahydroquinazolin-4-ones 264 (87TL115). 

Secologanin has been converted (by stages) into the hydrazone (110), which, on Bischler-Napieralsky ring-closure, reduction, and hydrolysis, yields protoemetine this was converted into cephaeline and deoxytubulosine by its reaction with (3-hydroxy-4- methoxyphenyl)ethylamine and with tryptamine respectively.138 The dithioacetal (111), prepared from norcamphor (see Volume... 

A newly discovered alkaloid, cherylline, has been shown to have a novel structure (5) derived from 4-phenylisoquinoline. It has been synthesised from the appropriate benzophenone by way of the alcohol, chloride, nitrile, and primary amine, followed by formylation, isoquinoline ring closure, reduction, and methylation. ... 

Ring closure, reductive -, electrochemical 26,80 -, review 26,158 -, monovalent 26,949 -, partial... 

Condensation of L-alanine with a heptaketide CoA thioester and concomitant decarboxylation gave compound 31, which was formed with overall retention of the absolute confguration. The same behavior was verified in reactions catalyzed by enzymes of the a-oxoamine synthetase family which depend on pyridoxal phosphate (PLP) as the cofactor. Ring closure, reduction of carbonyl at position 3, and subsequent elimination of water lead to 2//-azepine 33. The latest steps of the biosynthesis involve the modification of the side chain, leading to the carbonyl group of 30 [21],... 

Indolepropionic acids 19, 765 Indole ring closure, reductive... 

Reduction s. a. Clemmensen reduction. Elimination, reductive. Hydrogenation, Photoreduction, Ring closure, reductive -, asym., reversal of stereospecificity 17, 865 suppl. 28 -, electrodiemical -, S-debenzylation by -27,18 suppl. 28 -, N-detosylation by - 27, 18... 

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