Cleavage partial

Ring cleavage, partial desulfurization, and recombination of the intermediates... 

Peptide cleavage, partial hydrolysis of peptides and proteins by chemical ( end group analysis) or enzymatic methods (-> proteolysis) for sequence analysis. Limited peptide cleavage (limited proteolysis) is important for various metabolic processes. 

Ethylene derivatives by pyrolytic C-cleavage Partial detropylation... 

Nikiforov GB, Vidyaratne I, Gambarotta S, Korobkov I. Titanium-promoted dinitrogen cleavage, partial hydrogenation, and sdylation. Angew Chem Int Ed. 2009 48 7415-7419. 

This reaction has often reached explosive proportions in the laboratory. Several methods were devised for controlling it between 1940 and 1965. For fluorination of hydrocarbons of low (1—6 carbon atoms) molecular weight at room temperature or below by these methods, yields as high as 80% of perfluorinated products were reported together with partially fluorinated species (9—11). However, fluorination reactions in that eta involving elemental fluorine with complex hydrocarbons at elevated temperatures led to appreciable cleavage of the carbon—carbon bonds and the yields invariably were only a few percent. 

Hydantoins can react with electrophiles at both nitrogen atoms and at C-5. The electrophilic carbonyl groups can be attacked by nucleophiles, leading to hydrolysis of the ring or to partial or total reduction of the carbonyl system. Other reactions are possible, including photochemical cleavage of the ring. 

The pyrazole ring is particularly difficult to cleave and, amongst the azoles, pyrazoles together with the 1,2,4-triazoles are the most stable and easiest to work with. This qualitative description of pyrazole stability covers the neutral, anionic and cationic aromatic species. On the other hand, the saturated or partially saturated derivatives can be considered as hydrazine derivatives their ring opening reactions usually involve cleavage of the N—C bond and seldom cleavage of the N—N bond. It should be noted, however, that upon irradiation or electron impact the N—N bond of pyrazoles can be broken. 

Alkyl groups under nonacidic conditions sterically deflect nucleophiles from C, but under acidic conditions this steric effect is to some extent offset by an electronic one the protonated oxirane opens by transition states (Scheme 40) which are even more 5Nl-like than the borderline Sn2 one of the unprotonated oxirane. Thus electronic factors favor cleavage at the more substituted carbon, which can better support a partial positive charge the steric factor is still operative, however, and even under acidic conditions the major product usually results from Cp attack. 

In the main, the physical and chemical properties of saturated and partially unsaturated alicyclic compounds closely resemble those of the analogous acyclic compounds formally derived by cleavage of the carbon ring at a point remote from any functionality. Relatively small, but often significant, differences in properties arise from conformational effects, and from strain effects in small rings, and these differences can be striking in properties which are particularly sensitive to molecular shape. 

The Troc group on tryptophan is stable to CF3COOH, CF3SO3H, and H2 Pd, but can be cleaved with 0.01 M NaOH/MeOH, hydrazine/Me0H/H20, Cd/AcOH/DMF. Cleavage with Zn/AcOH is only partially complete. 

Dibromo-5a-3-ketones give A -2-bromo-3-ketohydrazones, which undergo partial cleavage with pyruvic acid, while 2,4-dibromo-3-ketones give mixed hydrazones which are not cleaved. 

According to Quinkert, photoexcited cyclic ketones may be transformed to open-chain unsaturated carboxylic acids in the presence of molecular oxygen. This reaction may compete efficiently with a-cleavage and secondary transformations thereof. Thus, both stereo iso meric 17-ketones (109) and (110) yield as much as 20% of the unsaturated acid (111) when irradiated in benzene under a stream of oxygen. This photolytic autoxidation has been used notably for partial syntheses of naturally occurring unsaturated 3,4-seco-acids from 3-oxo triterpenes (for references, see ref. 72). 

First, let us consider the formation of ions from covalently bound species, i.e., the heterolytic cleavage of the covalent (or partially covalent) bond. Charge separation under the influence of the solvent generates an ion pair in a process called ionization this ion pair may then separate into free ions in a dissociation step (Eq. 8-18). 

Solvolysis in MeOH/H20 at 21°. This method was developed for a series of penicillin derivatives where conventional cleavage methods resulted in partial /3-lactam cleavage. ... 

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