Homodienyl-l,5-hydrogen shift

This isomerization is most reasonably a homodienyl-l,5-hydrogen shift (see Chapter 7, Section 4), and the subsequent work by Srinivasan with methyl-labeled materials derived from photoaddition of cis- and trans-2-buicnQ to benzene across the meta positions confirmed that it was the endo hydrogen at C7 which was transferred. ... 

Bicyclo[6.1.0]nona-2,4-diene andbicyclo[6.1.0]nona-3,5-diene equilibrate at 180°C by 1,5-hydrogen shifts with the former being 2 kcal/mol more stable. However, the 2,4-diene undergoes a homodienyl-l,5-hydrogen shift to 1,4,7-cyclononatriene faster than it gives the 3,5-diene. The activation parameters for the interconversions are given in Scheme 10.45. ... 

The major product at low conversions is the result of a homodienyl-l,5-hydrogen shift, but it apparently reverts to starting material, which then undergoes non-concerted cyclopropane ring opening in either of two directions to give the bicyclic products (Scheme 10.64). 

The reaction involves a homodienyl-l,5-hydrogen shift, no doubt, via a saddle or folded conformation in order to generate a cis double bond in the product (See Chapter 7, Section 4). This result was subsequently confirmed. ... 

---

See also in sourсe #XX -- [ , , , , , , , , , , , , ]

---