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Nitrile Oxides, Nitrones, and Nitronates in Organic Synthesis : Novel ...

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B<br />

C<br />

A<br />

Closed [5,6] adduct<br />

B<br />

B<br />

KINUGASA REACTION ([2 + 2] CYCLOADDITION) 385<br />

A<br />

C<br />

A<br />

C<br />

Scheme 2.317<br />

Closed [6,6] adduct<br />

−<br />

A<br />

+ B<br />

C<br />

+<br />

+<br />

C<br />

Open [6,6] adduct<br />

−<br />

A<br />

B<br />

B<br />

C<br />

A<br />

Open [5,6] adduct<br />

−<br />

O<br />

H2C N+<br />

H<br />

economical <strong>and</strong> a facile way to the synthesis of β- lactams. Asymmetric K<strong>in</strong>ugasa<br />

reactions also provide an easy access to optically pure β-lactams (770)<br />

(Scheme 2.319) (842–847).<br />

Copper (II) salts proved to be efÞcient catalysts <strong>in</strong> the K<strong>in</strong>ugasa reaction,<br />

<strong>and</strong> this allowed the reaction to be performed under practical <strong>and</strong> convenient<br />

conditions. Am<strong>in</strong>es strongly <strong>in</strong>ßuence diastereoselectivity, enantioselectivity, <strong>and</strong><br />

reaction rate. Bulkier am<strong>in</strong>es always give better diastereoselection <strong>and</strong>, generally,<br />

tertiary am<strong>in</strong>es provide higher diastereoselectivity than secondary ones, <strong>and</strong> the

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