Asymmetric reduction with chiral organoboranes based on .alpha.-pinene

Brown, Herbert C.; Ramachandran, P. Veeraraghavan

doi:10.1021/ar00013a003

Cited by 184 publications

(79 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Although asymmetric hydroboration, [6,7] asymmetric allylboration, [8][9][10][11][12] and asymmetric boron-hydride reduction [7,13] were among the first asymmetric processes to be developed, these reactions have evolved into very valuable transformations for the enantioselective and diastereoselective synthesis of many types of molecules, particularly alcohols and amines. Several recent improvements and new asymmetric and catalytic variations have expanded significantly the utility of these processes.…”

Section: Expanding the Scope Of Boron-mediated Organic Reactionsmentioning

confidence: 99%

Expanding Roles for Organoboron Compounds – Versatile and Valuable Molecules for Synthetic, Biological and Medicinal Chemistry

Petasis

2007

Aust. J. Chem.

109

View full text Add to dashboard Cite

The present essay offers an overview of the latest developments in the chemistry of organoboron compounds. The unique structural characteristics and the versatile reactivity profile of organoboron compounds continue to expand their roles in several areas of chemistry. A growing number of boron-mediated reactions have become vital tools for synthetic chemistry, particularly in asymmetric synthesis, metal-catalyzed processes, acid catalysis, and multicomponent reactions. As a result, boronic acids and related molecules have now evolved as major players in synthetic and medicinal chemistry. Moreover, their remnant electrophilic reactivity, even under physiological conditions, has allowed their incorporation in a growing number of bioactive molecules, including bortezomib, a clinically approved anticancer agent. Finally, the sensitive and selective binding of boronic acids to diols and carbohydrates has led to the development of a growing number of novel chemosensors for the detection, quantification, and imaging of glucose and other carbohydrates. There is no doubt that the chemistry of organoboron compounds will continue to expand into new discoveries and new applications in several fields of science. Long History -Expanding RolesOrganic compounds containing boron have been known for over a century, and many aspects of their chemical properties and reactivity have been known for quite some time. Since the discovery and development of hydroboration, the resulting organoboranes are among the most widely used reagents and intermediates in organic synthesis including asymmetric reactions. Also, early investigations on the chemistry of boron hydrides and carboranes revealed new classes of compounds with unique structure and reactivity that continue to attract attention. Despite these early discoveries, however, the real potential of some of the more versatile and chemically stable organoboron compounds was not realized until recently.Indeed, the growing list of valuable organoboron compounds in addition to organoboranes [1] now includes organoboronic acids and boronates, [2] and more recently organotrifluoroborates.

show abstract

Section: Expanding the Scope Of Boron-mediated Organic Reactionsmentioning

confidence: 99%

Expanding Roles for Organoboron Compounds – Versatile and Valuable Molecules for Synthetic, Biological and Medicinal Chemistry

Petasis

2007

Aust. J. Chem.

109

View full text Add to dashboard Cite

show abstract

“…We next screened a wide variety of reagents for effecting the enantioselective reduction of 16 to (S)-17, the most satisfactory of which turned out to be (+)-DIP-Cl. 4 Even this reagent was not without its drawbacks, however. Thus, although (S)-17 was obtained with an ee >95%, experimental difficulties with the NaOH/HOOH cleavage procedure precluded its isolation in better than 45% yield.…”

Section: Resultsmentioning

confidence: 99%

“…), while maintaining a temperature of -78 °C. After addition was complete, the reaction was stirred at -78 °C for an additional 3 h and was then quenched with saturated NH 4 Cl and allowed to warm to r.t. The aqueous solution was then extracted with EtOAc, and the combined extracts were washed sequentially with 1 M HCl, H 2 O, saturated NaHCO 3 and brine.…”

Section: -(Tert-butyldimethylsilyl)but-2-yn-1-ol (25)mentioning

confidence: 99%

An improved synthesis of a ring-C precursor to cobyric acid

Jacobi¹,

Wang²

2010

Arkivoc

View full text Add to dashboard Cite

Alkyne acid 10 was prepared in enantioselective fashion from allylic ester derivative (R)-18 via an E-selective Ireland-Claisen rearrangement followed by Si-assisted elimination of HBr. The present route offers significant advantages in terms of both scalability and overall yield compared to that previously described. Alkyne acid 10 is an attractive ring-C precursor for an ongoing synthesis of cobyric acid.

show abstract

“…O (R)-alpino-borano (20) é largamente empregado na redução de cetonas como 21a-d , em que um dos substituintes da carbonila (R L ) seja muito mais volumoso do que o outro (R S ). Essas reações fornecem os correspondentes álcoois 22a-d em 44-100% de excesso enantiomérico [31][32] .…”

Section: Reagentes Quiraisunclassified

Abordagens em síntese assimétrica

Pinheiro¹,

Ferreira²

1998

Quím. Nova

View full text Add to dashboard Cite

Recebido em 5/11/96; aceito em 7/8/97 APPROACHES IN ASYMMETRIC SYNTHESIS. The approaches in asymmetric synthesis as the chiron approach, chiral auxiliaries, chiral reagents and asymmetric catalysis are described in a simplified way.Keywords: asymmetric synthesis; chiron approach; chiral auxiliary; chiral reagent; chiral catalyst. DIVULGAÇÃO INTRODUÇÃOUma das fronteiras atuais da química orgânica é a síntese assimétrica 1 , que objetiva a preparação de substâncias enantiomericamente puras (SEP) através da síntese exclusiva ou preferencial de um estereoisômero 2 . Dois enantiômeros podem apresentar ações diferenciadas sobre os organismos vivos, levando a diferentes sabores, odores, toxicidades e ações biológicas 3 . Tal enantiodiferenciação é baseada nas diferentes propriedades físicas dos diastereoisô-meros formados a partir da interação entre os enantiômeros de um substrato e os receptores biológicos, que são macromolécu-las quirais. Esta ação diferenciada dos enantiômeros de uma substância nos organismos vivos levou ao surgimento de processos industriais onde a pureza ótica é fundamental para a qualidade do produto, tais como: farmacêutica, alimentícia, de produtos agrícolas e perfumaria 4 . Em muitos casos a natureza não oferece SEP em quantidades suficientes para atender a demanda industrial. Em outros, muitas SEP de interesse econômico não são naturais 5 . Assim, no início da década de 70, a síntese assimétrica, em substituição à resolução de racematos, ganhou destaque como método para o acesso a SEP. De fato, hoje em dia certas substâncias são preparadas industrialmente através da síntese assimétrica, tais como o aspartame e a L-DOPA 2,6-8 . Essa tendência deverá ser incrementada em um futuro próximo, em função da crescente intenção dos químicos orgânicos sintéticos em efetuar versões enantiosseletivas das reações orgânicas de modo a mimetizar a ação das enzimas 9 . O objetivo desse trabalho é apresentar as abordagens utilizadas em síntese assimétrica, de forma a familiarizar aqueles que não estão envolvidos nessa área com o assunto e com a "linguagem assimétrica".A síntese assimétrica possibilita a criação de novos centros quirais durante as etapas de uma síntese. Desta forma, nesse texto serão excluídas outras metodologias para a obtenção de SEP 10,11 que não atendem a essa característica, tais como a resolução de racematos e o uso de blocos de construção quirais ("chiral building blocks").As abordagens utilizadas em síntese assimétrica incluem os usos de substratos quirais ("chiron approach") 12 e de substratos pró-quirais. Neste caso faz-se uso de auxiliares quirais, reagentes quirais e de catálise assimétrica 13 . Cabe ressaltar que, em todas essas abordagens, as substâncias quirais a serem empregadas nas sínteses (como substratos ou como auxiliares, reagentes ou catalisadores) são necessariamente produtos naturais ou seus derivados sintéticos visto que, em última análise, a natureza é a única fonte de substâncias quirais. Dentre as substâncias naturais, os carboidratos, terpenos, α-aminoácidos e os a...

show abstract

Asymmetric reduction with chiral organoboranes based on .alpha.-pinene

Cited by 184 publications

References 34 publications

Expanding Roles for Organoboron Compounds – Versatile and Valuable Molecules for Synthetic, Biological and Medicinal Chemistry

Expanding Roles for Organoboron Compounds – Versatile and Valuable Molecules for Synthetic, Biological and Medicinal Chemistry

An improved synthesis of a ring-C precursor to cobyric acid

Abordagens em síntese assimétrica

Contact Info

Product

Resources

About