A novel method for the synthesis of substituted naphthalenes and phenanthrenes

Ring-closing metathesis for the synthesis of substituted indenols, indenones, indanones and indenes: Tandem RCM-dehydrogenative oxidation and RCM-formal redox isomerization

“…A base-mediated method, using potassium tbutoxide, did result in the formation of the isomerized product 28b (R = Me), albeit in poor synthetic yields (44% on small scale and only 8% on a larger scale). The major problem with the use of potassium t-butoxide was that it led to the formation of unwanted naphthalene 30, a reaction previously exploited in our research group [59]. Finally, compound 28c (R = Ph) was formed directly from material 26c as described previously in the literature [59].…”

“…The major problem with the use of potassium t-butoxide was that it led to the formation of unwanted naphthalene 30, a reaction previously exploited in our research group [59]. Finally, compound 28c (R = Ph) was formed directly from material 26c as described previously in the literature [59]. Now with the three styrene-containing compounds in hand, the vinyl groups could be introduced by using the appropriate Grignard reagent to give dienes 29 (Scheme 4), required for the metathesis reaction.…”

“…The following substituted benzaldehydes were synthesised according to an established procedure [59]: 2-allyl-3-isopropoxy-4-methoxybenzaldehyde 27a (R 1 , R 2 = H) and 3-isopropoxy-4-methoxy-2-(1-methyl-2-propenyl)benzaldehyde 27b (R 1 = Me, R 2 = H).…”

“…The crude mixture was purified by column chromatography (5-10% EtOAc-hexane) to yield the desired product 28b as an orange oil (0.038 g, 8%, E/ Z ratio 4.3:1). In addition, a second, more predominant product (orange-brown oil) was recovered and this was found to be 5-isopropoxy-6-methoxy-4-methyl-1-naphthol 30 [59] (0.060 g, 12% relative to starting material). This reaction was originally done on a much smaller scale (0.10 g, 0.40 mmol of 27b) with KOBu t (0.049 g, 0.40 mmol) at 60°C and resulted in desired product 28b in 44% yield (0.044 g).…”

“…This reaction was originally done on a much smaller scale (0.10 g, 0.40 mmol of 27b) with KOBu t (0.049 g, 0.40 mmol) at 60°C and resulted in desired product 28b in 44% yield (0.044 g). 1 3-Isopropoxy-4-methoxy-2-(1-phenyl-1-propenyl)benzaldehyde 28c (R 1 = Ph) was synthesized according to a published procedure [59].…”