Chapter 24, Problem 24.38P

(a)

Interpretation Introduction

Interpretation:

Reasonable precursors have to be suggested for the formation of compound I in the given problem.

Concept introduction:

Amide bond formation:

Amides, commonly known as acid amides are those compounds which have $-\text{C(O)NHR}$ linkage.  Acid amides can be prepared in many ways and one of them is by coupling between carboxylic acid and amines with the help of DCC.  The mechanism is as follows,

(b)

Interpretation Introduction

Interpretation:

Reagents for the reaction along with the mechanism have to be given for the conversion of compound I to II as given in the question.

Concept introduction:

Coupling reaction of aryl halides and phenols catalyzed by palladium and MOP types of ligands:

Palladium catalyzed coupling reactions of aryl halides and phenols are described employing the bulky and electron rich MOP type ligands. When $\text{NaH}$ is used as base and ortho-xylene is used as a solvent unactivated aryl halides can be used as substrates.  When ${\text{K}}_{\text{3}}{\text{PO}}_{\text{4}}$ is used as base and toluene as solvent, the catalyst system exhibited high efficiency for the coupling reaction of the activated aryl halides.

(c)

Interpretation Introduction

Interpretation:

The two isomers of compound II have to be shown.

Concept introduction:

Atropisomers:

Atropisomers are the stereoisomers arising because of the hindered rotation about a single bond where energy differences due to steric strain or other contributors create a barrier to rotation that is high enough to allow for isolation of individual conformers.

(d)

Interpretation Introduction

Interpretation:

Suitable reagents have to be given for the transformation of compound II to III in the given problem.

Concept introduction:

Reduction of nitro group:

Reduction of nitro group can be done by various reagents.  In industrial scale reduction of nitrobenzene to anniline is a very common reaction.  It is done by catalytic hydrogenation in the presence of palladium hydrogen.

Diazotisation reaction:

Diazonium salta are organic compounds having $\text{R}-{\text{N}}_{\text{2}}^{\text{+}}{\text{X}}^{\text{-}}$ entity where R is alkyl or aryl group and X is mainly halide ion.  The diazo compounds can be formed by treatment of aromatic amines with nitrous acid and additional acid.  Usually nitrous acid is generated in. situ from sodium nitrate and excess mineral acid.  The reaction is done at very low temperature of ${\text{0}}^{\text{ο}}{\text{-5}}^{\text{ο}}\text{C}$.  The reaction is shown below,

Sandmeyer reaction:

The Sandmeyer reaction is a chemical reaction used to synthesize aryl halides from aryl diazonium salts using copper salts as reagents or catalysts.  It is an example of a radical nucleophilic aromatic substitution.  The Sandmeyer reaction provides a method through which the unique transformation on benzene such as halogenation, cyanation, trifluoromethylation and hydroxylations can be done.

(e)

Interpretation Introduction

Interpretation:

The reagents and the fragment of the ring A that is useful for the conversion of compound III to IV have to be given.

Concept introduction:

Grignard reaction:

A grignard reagent is a chemical compound with the formula $\text{R}-\text{Mg}-\text{X}$ where R is alkyl or aryl groups and X is halogen.  The coupling reaction between unreacted bromobenzene and grignard reagent gives biphenyl kind of product.  Formation of this product needs more heat.

(f)

Interpretation Introduction

Interpretation:

Ring closure reaction of the deprotected free amino group has to be given along with the mechanism.

Concept introduction:

Amide bond formation:

Amides, commonly known as acid amides are those compounds which have $-\text{C(O)NHR}$ linkage.  Acid amides can be prepared in many ways and one of them is by coupling between carboxylic acid and amines with the help of DCC.  The mechanism is as follows,

(g)

Interpretation Introduction

Interpretation:

The atropisomers have to be drawn and also it has to be shown that only one of them can be converted to vancomycin.

Concept introduction:

Atropisomers:

Atropisomers are the stereoisomers arising because of the hindered rotation about a single bond where energy differences due to steric strain or other contributors create a barrier to rotation that is high enough to allow for isolation of individual conformers.