Scheme 14.

Effect of Diene Geometry on Diastereoselectivity.^a

^a Compare with Scheme 6. Reactions were run on 0.4 mmol scale with 5 mol% [Fe] precatalyst. Product ratios determined by gas chromatographic analysis and corroborated by relative integration of diagnostic resonances in the quantitative ¹³C NMR spectrum of the isolated material. ^b 98% [4+4] selectivity ^c 77% [4+4] selectivity ^d no 3b or 4b detected ^e <10% combined yield of dimeric products with 65% [4+4] selectivity, 74:26 3b : 4b ^d 30% combined yield dimeric products with 98% [4+4] selectivity; 44% yield iso-1b ^e 62% combined yield of dimeric products with 60% [4+4] selectivity; 38% yield iso-1b