Hydrogenolysis carbonyl substituted

The Gassman indole synthesis involves a one-pot process in which a hypohalite, a P-carbonyl sulfide derivative, and a base are added sequentially to an aniline or a substituted aniline to provide 3-thioalkoxyindoles. The sulfur can be easily removed by hydrogenolysis or Raney nickel. 

In order to prevent hydrogenolysis of the benzylidene group, Kalra substituted methanol in place of hydrogen other workers had previously shown that, by this modification of the oxo reaction, carbonyl insertion occurs in epoxides, with the formation of esters. - When the same substrate (75) was treated with carbon monoxide and methanol at 190 , the preponderant products were those formed by methanolysis and hydrolysis, with preponderant, tmns-diaxial opening of the epoxide, to give, in 30% yield, methyl 3-O-methyl-a-D-altropyranoside (78) and, in 26 % yield, methyl 4,6-O-benzylidene-a-D-altropyranoside (79). Part of the reaction product (15%) consisted of unchanged substrate, and there was evidence (from mass-spectral studies) that a carbonyl insertion had taken place to a very negligible extent (less than 5 %). 

This chapter surveys the reduction of saturated alkyl halides to alkanes. Reductive -eliminations of vicinal dihalides to alkenes are also described briefly. Reduction of vinyl and aryl halides is covered in this volume. Chapter 4.5 hydrogenolysis of allyl and benzyl halides is covered in this volume. Chapter 4.7, and reduction of a-halo-substituted carbonyl compounds CX—CO to carbonyl compounds CH—CO is covered in this volume. Chapter 4.8. 

Substituted hydrazines. Carbonyl compounds undergo reductive condensation with this reagent, which is prepared from 1,2-di-f-Boc-l-tosylhydrazine by selective hydrogenolysis. 

Cii. The carbonyl group of 3 is converted to an endo-methyl group by addition of CHjLi followed by ionic hydrogenolysis to provide the complex 4. Reaction of 4 with 2-lithio-l,3-dithiane results in substitution meta to the methyoxy group to provide 5 after demetalation. This product has the desired rra/is-arrangement of the groups at Ci and C4 as well as the precursor for the carboxyl group at for the complete synthesis of the diterpene 6. The conversion of 5 into 6 was completed in four conventional steps. 

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