連続サイクロブタンC-Hアリレーションによるパイパーボレニンの総合成と構造修正
Will R Gutekunst1, Phil S Baran
1Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Journal of the American Chemical Society
|November 10, 2011
まとめ
この研究は,パイパルボレニンBとDの全合成によって例示される非対称なサイクロブタンを合成するための新しいC-H機能化戦略を提示しています.これは,シス-サイクロブタン二酸化炭素酸塩の準備と制御されたアリルリングの設置のための新しい方法を導入しています.
科学分野:
- 有機化学 オーガニック・ケミストリー
- 合成化学 合成化学とは
- 自然製品合成 自然製品の合成
背景:
- 非対称なサイクロブタンは,天然製品の貴重な構造モチーフです.
- 複雑なサイクロブタンの誘導体への効率的な合成経路は,依然として課題です.
研究 の 目的:
- 非対称なサイクロブタンを構築するためのC-H機能化戦略を開発する.
- パイパルボレニンBとパイパルボレニンDの全合成を達成するために.
- シス-サイクロブタン二カルボキシラート製剤とステレオ選択C-Hアリレーションのための新しい方法を探求する.
主な方法:
- パイパルボレニンBとDの総合成.
- コムラート起料からシス・サイクロブタン・ディカルボキシラートのための新製剤の開発.
- アリル環の制御された設置のためのサイクロブタンC-Hアリレーションの適用.
- ダイマー合成のための分子内 [2+2] フォトサイクロアディション.
主要な成果:
- 非対称サイクロブタン合成のためのC-H機能化戦略を実証した.
- シス・サイクロブタン二炭酸塩酸への新たな経路を確立しました.
- アリル置換剤の制御された cis または trans 設置を達成しました.
- パイパルボレニンDの構造をヘッドツーヘッドジマーに再割り当て,それを合成した.
結論:
- 開発されたC-H機能化ロジックは,非対称なサイクロブタン構造のための強力なツールを提供します.
- 合成戦略は,複雑な天然製品への異なるアクセスを可能にします.
- パイパルボレニンDの再配分と合成は,光環添加戦略の有用性を強調しています.
関連する概念動画
01:18Aromatic Hydrocarbon Cations: Structural Overview
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group with both...
Removing one hydrogen from the intervening CH2 group with both...
![[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12422.jpg&w=3840&q=75)
01:21[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement
The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
01:27Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).
02:27Preparation of Alkynes: Alkylation Reaction
Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
02:36Regioselectivity and Stereochemistry of Hydroboration
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.