Overman Rearrangement of γ- Aryl Crotyl Alcohols: Effects of Aryl Substituents

Cho, Cheon‐Gyu; Lira, Yeong-Kwan; Lee, Kang-sang; Jung, In-Hak; Yoon, Moon-Yeong

doi:10.1080/00397910008087201

Cited by 14 publications

(4 citation statements)

References 14 publications

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“…With both syn-and anti-bisA C H T U N G T R E N N U N G (imidate)s 12 in hand, we then investigated the cascade-type Overman rearrangement (Table 3). A solution of (Z)-syn-bisA C H T U N G T R E N N U N G (imidate) 12 a and tertbutylbenzene in the presence of Na 2 CO 3 [11] was heated at 200 8C in a sealed tube, thus giving anti-bisA C H T U N G T R E N N U N G (amide) 14 a in 95 % yield ( Table 3, entry 1). The reaction proceeded with complete diastereoselectivity.…”

Section: Resultsmentioning

confidence: 99%

“…However, cyclic orthoamide 13 a had significantly decomposed, owing to the prolonged reaction time ( Table 4, entry 1). Then, the effects of standard basic additives, such as K 2 CO 3 [12] and Na 2 CO 3 , [11] on the Overman rearrangement were investigated ( Table 4, entries 2 and 3). Whilst the addition of K 2 CO 3 led to a low yield, the less basic Na 2 CO 3 had some positive effects in preventing the decomposition pathway.…”

Section: Resultsmentioning

confidence: 99%

“…Selective formation of bisA C H T U N G T R E N N U N G (imidate)s(12) and cyclic orthoamides (13) from anti-vicinal diols(11). [a] …”

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confidence: 99%

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Cascade‐ and Orthoamide‐Type Overman Rearrangements of Allylic Vicinal Diols

Nakayama

Sekiya

Oishi

et al. 2013

Chemistry A European J

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This article describes the details of two new types of Overman rearrangement from allylic vicinal diols. Starting from identical diols, both bis(imidate)s and cyclic orthoamides were selectively synthesized by simply changing the reaction conditions. Whilst exposure of the bis(imidate)s to thermal conditions initiated the double Overman rearrangement to introduce two identical nitrogen groups in a single operation (the cascade-type Overman rearrangement), the reaction of cyclic orthoamides resulted in a single rearrangement (the orthoamide-type Overman rearrangement). The newly generated allylic alcohols from the orthoamide-type reaction can potentially undergo a variety of further transformations. For instance, we demonstrated an Overman/Claisen sequence in one pot. The most conspicuous feature of this method is that it offers precise control over the number of Overman rearrangements from the same allylic vicinal diols. This method also excludes the tedious protecting-group manipulations of the homoallylic alcohols, which are necessary in conventional Overman rearrangements. All of the performed rearrangements proceeded in a completely diastereoselective fashion through a chair-like transition state.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Cascade‐ and Orthoamide‐Type Overman Rearrangements of Allylic Vicinal Diols

Nakayama

Sekiya

Oishi

et al. 2013

Chemistry A European J

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“…As olutiono f11 in tBuPh in as ealed tube was heated to 180 8Cinthe presence of MS4 , giving allylic alcohol 22 throughe quilibrium with imidate 21.A fter the consumption of 11 was confirmed by TLC, trimethyl orthoacetate and 2nitrophenol werea dded to the resulting allylic alcohol 22 in ao ne-pot operation. The sequential rearrangement took place in complete diastereoselective fashion, and gave the rearrangedp roduct 12 in 54 %y ield as as ingle diastereomer.T he standarda dditives utilized in the Overman rearrangement, such as K 2 CO 3 [19] and Na 2 CO 3 , [20] resulted in significant decompositiona th igh reaction temperature due to the relatively strong basicity.H owever, addition of MS4 s uppressed the decomposition pathway in the orthoamide-type Overman rearrangement. Although the role of MS4 h as not yet been eluci- dated, it might operatea samild base rather than as ad ehydrating reagent.…”

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Enantioselective Total Synthesis of (+)‐Neostenine

Nakayama

Maeda

Kotatsu

et al. 2016

Chemistry A European J

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A chirality transfer approach using acyclic polyol intermediates for the synthesis of (+)-neostenine (1) has been developed. The sequential Overman/Claisen rearrangement of an allylic 1,2-diol was especially useful, installing two contiguous stereocenters with complete diastereoselectivity in a one-pot sequence. The SmI -mediated cyclization and the subsequent chemoselective reduction of a lactam moiety accomplished the first enantioselective total synthesis of (+)-neostenine (1).

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The Allylic Trihaloacetimidate Rearrangement

Overman

Carpenter

2005

Organic Reactions

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Sigmatropic rearrangements of allylic systems have found wide application in organic synthesis, with carbon‐carbon bond forming rearrangements such as the Cope and Claisen rearrangements being particularly well known. The sigmatropic rearrangement of allylic imidates offers a valuable entry into the preparation of protected allylic amines. Conversion of an imidate to the amide is essentially irreversible, with the transformation of the imidate to the amide being exothermic by about 15 kcal/mol. Since the discovery of the thermal allylic imidate rearrangement in 1937, a number of systems have been investigated for the practical preparation of allylic amines by this route. However, it was the discovery and development of the rearrangement of allylic trichloroacetamidates that demonstrated the utility of this synthetic method. This chapter is limited to the discussion of allylic trichloro‐ and trifluoracetamidate rearrangements. The [3,3]‐sigmatropic rearrangement of trichloracetamidates (now called the Overman rearrangement) or trifluoroacetimidates can be carried out either thermally or with Hg(II) or Pd(II) catalysis, The scope of this rearrangement is such that primary, secondary, and tertiary allylic amides are readily accessible, thus providing a wide entry into nitrogen‐containing products such as amino sugars, nucleotides, peptides, etc. The Overman rearrangement has found extensive application in the total synthesis of natural products. The recent development of the use of chiral Pd(II) catalysts bodes well for amine synthesis.

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Overman Rearrangement of γ- Aryl Crotyl Alcohols: Effects of Aryl Substituents

Cited by 14 publications

References 14 publications

Cascade‐ and Orthoamide‐Type Overman Rearrangements of Allylic Vicinal Diols

Cascade‐ and Orthoamide‐Type Overman Rearrangements of Allylic Vicinal Diols

Enantioselective Total Synthesis of (+)‐Neostenine

The Allylic Trihaloacetimidate Rearrangement

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