Bicyclo heptanes, fragmentations

On the other hand, acyclic diastereomers are not necessarily compounds without any cyclic structural element, but the fragment connecting the stereogenic centers is acyclic. For example, a bicyclo[2.2.1]heptane derivative with a chiral side-chain attached to a nonbridgehead carbon belongs to this second category of acyclic diastereomers. 

Table 13. Cycloheptenones by Grob- Wharton Fragmentation of Bicyclo[3.2.0]heptan-l-ol Derivatives...

Bicyclo i.2.0)heptane-2-ols (2) cyclopentenones.1 Photobicyclization of 1,6-hcptadicnc-3-ols (1) in the presence of CuOTf results in bicyclo(3.2.0)heptane-2-ols (2) in 70-85% yield. The corresponding ketones readily fragment to ethylene and cyclopentenones (4) when heated in a quart/ tube at 600. ... 

Applying these pieces of information to the mass spectrum of bicyclo[2.2.1]heptane (Fig. 8.11), we can identify fragment peaks due to the loss of the side chain (the one-carbon bridge, plus an additional hydrogen atom) at mie = 81 and the loss of ethene at m/e = 68. The fragment ion peak at m/e = 61 is due to the loss of ethene plus an additional hydrogen atom. 

Fragmentations of bicyclo[3.2.0]heptanes are commonly used to prepare seven-membered rings. The value of this process arises from... 

Let us describe some frequently encountered polycyclic structures. Bicyclo[2.2.1] heptane, also known as norbomane, is the basic structure of a series of natural products. The tricyclic compound adamantane (tricyclo[3.3.1.L ]decane) is in principle the smallest structural fragment of diamond and its structure appears on the list of pharmaceutically important products. Adamantane was synthesized for the first time in 1941 at the University of Zagreb by Vladimir Prelog. 

CuOTf-catalyzed photobicyclization of l,6-heptadien-3-ols produces bicyclo[3.2.0]heptan-2-ols (eq 27). In conjunction with pyrolytic fragmentation of the derived ketones, these CuOTf-catalyzed photobicyclizations provide a synthetic route to 2-cyclo-penten-l-ones from l,6-heptadien-3-ols (eq 28). The derived... 

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