Synthesis of Chiral Propargylamines, Chiral 1,2‐Dihydronaphtho[2,1‐b]furans and Naphtho[2,1‐b]furans with C‐Alkynyl N,N′‐di‐(tert‐butoxycarbonyl)‐aminals and β‐Naphthols

Abstract

Chiral phosphoric acid-catalyzed couplings of Calkynyl N, N'-di-(tert-butoxycarbonyl)-aminals with β-naphthols led to chiral propargylamines in moderate to high yields with high to excellent enantioselectivity, in which the reactions underwent sequential chiral phosphoric acid-catalyzed in situ formation of N-(tert-butoxycarbonyl)-imines (N-Boc-imines) from the aminals, and 1,2-addition of β-naphthols to the N-Boc-imines. Chiral 1,2-dihydronaphtho[2,1-b]furans and naphtho[2,1-b]furans were prepared with satisfactory results when 10 mol% AgOAc and 20 mol% 2,6-lutidine or 1.2 equiv. of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were added to the resulting chiral propargylamines solution, respectively.

An overview of the applications of chiral phosphoric acid organocatalysts in enantioselective additions to CO and CN bonds

“…Following a similar approach, in 2021, Fu and co-workers reported the addition of 2-naphthols 136 to N , N -propargyl aminals 135 (Scheme 39) in the presence of catalyst ( R )- BPA1 . 133 Despite the high temperatures required for this transformation, the reaction affords highly enantioenriched propargylamines 137 (53–84%, 86–96% ee). Moreover, the subsequent ‘one-pot’ cyclization reaction leads to the formation of benzofuran derivatives 138 in similar yields and enantiocontrol (56–80%, 80–98% ee).…”

Progress on the Synthesis and Applications of Aminals: Scaffolds for Molecular Diversity

“…121 Considering N-Boc aminals as efficient imine surrogates (Scheme 30), it is noteworthy the use of N-Boc aminals as an alternative to forge less accessible alkenyl N-Boc imines and alkynyl N-Boc aminals. 122 The latter was explored in the a-b) functionalization of imines through Mannich reactions, 122,123 bc) Mukayama-Mannich reaction, 122,124 d) Friedel-Crafts reaction of indoles, 125 e-g) synthesis of propargylic amines, [126][127][128] h) aza-Mannich, 129 and i) BF3-catalyzed [2+4] cycloadditions. 130 Scheme 30 Applications of N-Boc aminals as imine surrogates.…”

Organocatalytic (Z/E)-Selective Synthesis of 3-Vinylnaphthofurans via a Formal (3 + 2) Cycloaddition

“…Moreover, R7000 with a naphthofuran core serves as a candidate antiparasitic drug, and compound I showed significant anticancer activity against human cancer cell lines. As a consequence, great attention has been paid to develop efficient approaches for the construction of naphthofuran scaffolds. − Among them, metal-catalyzed reactions − and organocatalytic reactions are generally the most effective methods toward the synthesis of naphthofurans, which resulted in the rapid development of synthetic methods for naphthofurans.…”