Meta-Chloro

The molybdenum-mediated arylamine cyclization was also applied to the total synthesis of pyrano[3,2-a]carbazole alkaloids (Scheme 26). Reaction of the 5-aminochromene 71 with the complex salt 62 affords the complex 72, which on oxidative cyclization provides girinimbine 73, a key compound for the transformation into further pyrano[3,2-a] carbazole alkaloids. Oxidation of 73 with DDQ leads to murrayacine 74, while epoxidation of 73 using meta-chloro-perbenzoic acid (MCPBA) followed by hydrolysis provides dihydroxygirinim-bine75 [113]. 

TBS = tributyl silyl m-CPBA = meta-chloro peroxy benzoic acid... 

The values of pfCa given in the following table have been observed for the parent compounds and for the meta-chloro- and the mefa-nitro-substituted compounds. 

The epoxide 6 is naturally electrophilic, but where does the epoxide come from By far the most important method of epoxide synthesis is the treatment of alkenes 19 with peroxy acids RCO3H 21. Alkenes are naturally nucleophilic 2 they react with bromine to give dibromides 20 and with electrophilic peroxyacids 21 to give epoxides. Again, these reactions convert nucleophilic alkenes into electrophilic derivatives. A very popular reagent for epoxidation is mCPBA (meta-chloro-perbenzoic acid) 21 R = 3-chlorophenyl but many other compounds are used. 

Scheme 13. The seleno linkage in 56 and a 1,2-seleno-migration (56—>57) provided access to 2-deoxy-saccharides such as 60 and orthoesters such as 61 (mCPBA, meta-chloro perbenzoic acid DAST, diethylamonium sulfur trifluoride).

Fig. 14.36. Regioselective Baeyer-Villiger rearrangement of an unsymmetrical ketone with HCPBA (meta-chloro-peroxybenzoic acid). The aryl group is [l,2]-shifted in all cases and irrespective of whether the acetophenone is electron-rich or electron-poor.

Davey, R.J. Garside, J. Hilton, A.M. Mcewan, D. Morrison, J.W. Emulsion solidification of meta-chloro-nitrobenzene purification and crystallization. J. Cryst. Growth 1996, 166 (1 ), 971-975. 

When TS-1 was used as the catalyst the selectivity to the triol product was very low and only became significant at extended reaction times. When the homogeneous stoichiometric oxidant meta-chloro-perbenzoic acid was used it is apparent that the selectivity to the triol was significant even at short reaction times. The low triol selectivity observed with TS-1 is considered to be due the hydrophobic nature of the titanium silicate framework. 

Draw resonance contributors for the carbanion that would be formed if meta-chloro-nitrobenzene could react with hydroxide ion. Why doesn t it react ... 

The importance of this reaction relies on the fact that the Betti bases can function as both excellent ligands and auxiliaries in asymmetric synthesis. The racemic Betti amines can be separated into their optical antipodes. In this respect, among the Betti bases from monochlorobenzaldehydes, only the dextro form of the ortho and meta chloro compounds could be resolved with satisfaction, while the levo antipodes are extremely difficult to obtain due to their higher solubilities. ... 

In 1934 Saxton and Meier [1] published a report in which they described measurements of the acid dissociation constants of benzoic acid and its three monochloro derivatives. The results showed an interesting pattern all of the chloro-derivatives were more acidic than the parent compound, with the ortlio-substituted compound most acidic and the meta-chloro derivative least acidic. However, the authors closed their report with the lament that at present, there is no adequate theoretical method of calculating the ionization of a weak electrolyte from its structure. ... 

HT uptake in vitro and in vivo, and (7) potentiates 5-HTP. Cardiac arrhythmia is not observed, and peripheral anticholinergic activity is equal to or less than that of imipramine. The meta-chloro analogue is in vivo an even more active 5-HT... 

This step looks for a meta chloro substituent and if it finds one, adds 0.37 to the value in the accumulator. 

Figure 6 The GENIE Control Language for modeling the effect of a meta-chloro substituent on the pK of a benzoic acid.

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