Substitution Controlled Functionalization ofortho-Bromobenzylic Alcohols via Palladium Catalysis: Synthesis of Chromenes and Indenols

Abstract

An efficient domino Pd-catalyzed transformation of simple ortho-bromobenzyl tertiary alcohols to chromenes is presented. Their formation is believed to proceed via the formation of a five-membered palladacycle, which, in turn, involves in an intermolecular homocoupling with the second ortho-bromobenzyltertiary alcohol to yield the homo-biaryl bond followed by intramolecular C-O bond formation. Interestingly, when there is an allylic substituent on the benzylic carbon atom, a chemoselective switch was observed, which preferred intramolecular Heck coupling and gave indenols. Further, it has been confirmed that the tertiary alcohol functionality is indispensible to give the coupled products, whereas the use of primary/secondary benzylic alcohols furnished the simple carbonyl products via a possible reductive debromination followed by oxidation due to the availability of β-hydrogen(s).

Synthesis of Enantioenriched 5,6‐Dihydrophenanthridine Derivatives through retro‐Carbopalladation of Chiral o‐Bromobenzylamines

“…It should be noted that when primary or secondary o ‐bromobenzyl alcohols were employed, β‐H elimination of the palladacycle A occurred to give the carbonyl products 3 [Eq. (1), Scheme ] 3a. Based on these interesting observations and our previous work on the Catellani reaction,4 in which formation of Pd IV intermediate and retro‐carbopalladation of norbornene are two of the key steps,5 we anticipated that 5,6‐dihydrophenanthridine derivatives 7 , which are prevalent structural units in natural products and biologically active molecules,6, 7 might be accessible if o ‐bromobenzylamines 6 undergo a similar Pd‐catalyzed homocoupling reaction as that of o ‐bromobenzyl alcohols 1 [Eq.…”

Recent Advances in the Synthesis of Indanes and Indenes

“…A possible reaction pathway involves a β‐hydrogen elimination from the carbinol group at level of intermediate 70 , followed by tautomerization of the resulting enol (Scheme ) . Interestingly, a similar reaction of 1‐(2‐bromophenyl)‐3‐en‐1‐ols led to the formation of an inseparable mixture of 3‐methyleneindan‐1‐ols (from Heck cyclization), 3‐methyl‐1 H ‐inden‐1‐ols (from isomerization of 3‐methyleneindan‐1‐ols) and 1‐methylene‐1 H ‐indenes (from dehydration of 3‐methyl‐1 H ‐inden‐1‐ols) …”

Catalytic Chemical Amide Synthesis at Room Temperature: One More Step Toward Peptide Synthesis

“…The 1 H and 13 C data were consistent with those reported in the literature. 31 N-Hexyl-2-phenylacetamide (20). The title compound is known and described.…”