Chemistry Reference
In-Depth Information
Scheme 8.15 Cation-
p
cyclization.
presented as capable of replacing the carbon-oxygen double bond of aldehydes and
ketones with carbon-carbon double bonds. The new extensions can be simple or functio-
nalized. Additionally, the newly formed double bonds can be modified through addition of
halogens or acids.
One final example of a name reaction presented within the text of this topic is the
cation-
p
cyclization. This reaction, illustrated in Scheme 8.15, returns to the previously
described reaction classes that include electrocyclic reactions and rearrangements.
Inclusion of this reaction complements the various nucleophiles used throughout the
examples of this topic by highlighting the nucleophilic nature of double bonds.
As will be revealed through further coursework, many more name reactions are avail-
able. Furthermore, new reactions, yet to be named, are continually being discovered. In
approaching all of these reactions, it is imperative to develop mechanistic understandings
in order to correctly apply the reactions within the scope of their utilities and limitations.
In this respect, arrow pushing presents a valuable approach to the derivation of mechanistic
understanding prior to committing the reaction names to memory.
8.3 REAGENTS
Throughout this topic, and in association with the various reactions presented, various
reagents were presented that, due to their specific properties, react in very specific ways.
These reagents differ in their basicity, nucleophilicity, and preferred sites of reaction.
Table 8.1 summarizes the various properties of the reagent classes presented.
Of the reagents listed in Table 8.1, dialkyllithiocuprates stand out because of
their unique ability to participate in 1,4-addition reactions. Such reactions, also known as
conjugate additions, are generally referred to as Michael additions. This name
reaction is illustrated in Scheme 8.16 with the reaction of dimethyllithiocuprate with
methyl vinyl ketone.
When considering the reagents listed in Table 8.1, it is important to remember that this
table is not inclusive. There are many permutations of the reagents listed in the table as
well as innumerable additional reagents that have been made useful to various aspects
of organic chemistry. In fact, many research groups focus exclusively on the design and
preparation of novel reagents capable of solving difficult synthetic problems. It is
through this aspect of organic chemistry that some of the most significant advances
have been realized.
