Tetramic adds

Condensation of acetyl-tetronic or -tetramic acids with methyl- or phenyl-hydrazine leads to 3-(l-hydrazinoethyl)-tetronic and -tetramic add, respectively, which upon dehydration form 1-substituted 4-oxo-l,4-dihydro-6//-furo[3,4-c]pyrazoles (X=0) and -pyrrolo[3,4-c]pyrazoles (X=NH) (equation 20) (82SC431). 

Gitlerman CO (1965) Antitumor, Cytotoxic, and Antibacterial Activities of Tenuazonic Acid and Congeneric Tetramic Adds. J Med Chem 8 483... 

Aoki, S., Higuchi, K., Ye, Y, Satari, R., and Kobayashi, M. (2000) Melophlins A and B, novel tetramic adds reversing the phenotype of ras-transformed cells, from the marine sponge Mdophlus sarassinorum. Tetrahedron, 56,1833—1836. 

Matsunaga, S Fusetani, N., Kato, Y., and Hirota, H. (1991a) Aurantosides A and B cytotoxic tetramic add glycosides from the marine sponge Theonella sp. J. Am. Chem. Soc., 113, 9690-9692. 

When catalyzed by acids, low molecular weight aldehydes add to each other to give cyclic acetals, the most common product being the trimer. The cyclic trimer of formaldehyde is called trioxane, and that of acetaldehyde is known as paraldehyde. Under certain conditions, it is possible to get tetramers or dimers. Aldehydes can also polymerize to linear polymers, but here a small amount of water is required to form hemiacetal groups at the ends of the chains. The linear polymer formed from formaldehyde is called paraformaldehyde. Since trimers and polymers of aldehydes are acetals, they are stable to bases but can be hydrolyzed by acids. Because formaldehyde and acetaldehyde have low boiling points, it is often convenient to use them in the form of their trimers or polymers. 

The second example is more reasonable but 3-phenyl-l,3-oxazetidin-3-one is obtained in low yield from formaldehyde tetramer and phenyl isocyanate (Scheme 92) (67TL3637). Perhalogenated (F or Cl) ketones also add to methylisocyanate catalyzed by CsF, BF3 or in liquid S02 solvent in 5-70% yield (67JOC2960). Dichloroethylene is reported to add to benzoyl isocyanate in 23% yield, also by addition across the carbon-oxygen bond of the isocyanate (70BAU1479). 

Low molecular weight lignin model compounds (synthetic phenyl-tetramers and Igepals ) were found to fit universal calibration. Fractions from preparative GPC, when analyzed by universal calibration, yield molecular weight distributions which add to a similar value to that found for the unfractionated parent sample. 

A major method for the preparation of y-amino-()-hydroxy adds of syn configuration is the stereocontrolled reduction of enantiomerically pure tetramic acids 32, followed by alkaline or acid hydrolysis of the resulting N-protected 4-hydroxy lactams 33 (Scheme 9))53-571... 

The mechanism in Scheme 1 accounts for the sequential formation of oligomers. The tetramethyldisiloxane (E E or TMDS) adds to 30 in Step C. Subsequent reductive elimination (Step D) produces the trimer E DE. As the concentration of E DE increases, the trimer can oxidatively add to 30 in Step C, producing the tetramer E DzE, and so on. 

Alcohols are used in the synthesis of metsJ hydrides where metal alkoxides are intermediates. Isolation of hydridometal alkoxides from the oxidative addition of alcohols to metal centers is not common. Hydrocarbon solns of WjCNMej) and 2-propanol generate" NHMe and H at RT. The product results from alcoholysis, oxidative addition of i-PrOH and condensation to the tetramer, H W COPr-i),. Both Os3(CO),2 and Os3(NCMe)2(CO),g oxidatively add HOR (R = Me, Et), forming HOs3(OR)(CO)3q. Phenol adds to Ni[P(C H,)3]2 under mild conditions to yield HNi(OPh)[P(C,H )3]2. 

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