Hydroboration as a Convenient Procedure for the Asymmetric Synthesis of Alcohols of High Optical Purity

Brown, Herbert C.; Zweifel, George

doi:10.1021/ja01463a055

Cited by 78 publications

(89 citation statements)

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“…This oxirane was prepared by partial asymmetric destruction of 2-vinyioxirane with di-3-pinanylborane by adaption of the procedure of Brown and Zweifel (18). A mixture of sodium borohydride (0.165 g, 0.0044mol), (+)-a-pinene (1.36 g, 0.01 moll Aldrich, a, +43.5", neat), and diglyme (10 ml) was stirred and cooled under a nitrogen atmosphere in an ice bath.…”

Section: (-)-(R)-2-vlnyloxiranementioning

confidence: 99%

The thermally induced rearrangements of 2-vinyloxirane

Crawford¹,

Lutener²,

Cockcroft³

1976

Can. J. Chem.

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. Can. J. Chem. 54, 3364 (1976).The kinetics of the gas phase thermoiysis of Zvinyloxirane (4) have been studied over the temperature range 270-310 "C. The racemization of chiral 4 occurs six times faster than the structural ison~erization to 2,3-dihydrofiran, (E)-and (d)-2-butenai, and 3-butenal. The butenals undergo a slow ihermolysis to propene and carbon monoxide. cis-Deuterio-and frnr2s-3-deuterio-vhyioxirai1~ have been synthesized and their interconversion is slow. Deuterium kinetic isotope ezects on motzo-and dideurerio-4 suggest that for the formation of the kutenals the rate determining step involves rupture of the oxirane C-0 bond. The dihydrofuran is produced by thermolysis of the oxirane C-C bond. The preferred mechanistic interpretatiur, is that a carbon-oxygen diradical serves as an intermediate for butenal formation, and that a carbonyi-ylide is involved in the formation of the dihydrofuran.Tile relative rates, at 307.4 " C , of cis-irans-isomerizatim:diI1ydrofuran formation: racemization: butenal formation for 3-dcuterio-2-vinyloxirane are On a CtudiC, B des ten~pCratures ai!ant de 270-310 'C, la cinktique de ia thermolyse en phase gazeuse du vinyl-2 oxiranne (4). La racCrnisation du composk 4 chiral se pioduib 6 fois plus rapidemnt que I'isorn6risation de structure en dihydro-2,3 furanne, en butkne-2 als ( E ) et ( Z ) el en Sutkne-3 al. Les butenais subissent !me therinolybe lente conduisant au propkne et au monoxyde de carbone. On a aussi syntbCtisC les deutCrio-3 vinyloxirannes cis et trans et !cur interconversion est lente. Ees effets isotopiques cinktiques du deuterium sur les motlo-et diderlririo 4 suggkrent que, pour la formation des butknals, I'etape dCtermiriant la vitesse de la rCaction irnplique la rupture du lien C--0 de l'oxiranne. Le dihydrofuranne se produit par thermolyse du lien C-C de i'oxiranne. L9interprCtation mkcanistique prCf6rCe implique qu'il y a formation d'un diradical carbone-oxygkne comnle interinkdiaire pour la formation des butenais et qu'un carbonyl-yfide est irnplique dans la formation de la dihydrofuranne. kes vitesses relatives, B 307.4 "C, pour I'isomCrisation cis-tratzs: la formation de dilvdrohranne: la rackmisation: la formation de butenal B partir du de~lterio-3 vinyl-2 oxiranne sont respectivement de 1.0:0.88 :40.2:5.94.[Traduit par le journal]

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Section: (-)-(R)-2-vlnyloxiranementioning

confidence: 99%

The thermally induced rearrangements of 2-vinyloxirane

Crawford¹,

Lutener²,

Cockcroft³

1976

Can. J. Chem.

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“…C. Browns dramatic enantioselectivities observed in the hydroboration of alkenes in 1961 using (À)-diisopinocamphenylborane [(Ipc) 2 BH] heralded the birth of asymmetric synthesis (Scheme 1 a). [1] He showed for the first time that simple chiral reagents of low molecular weight were capable of inducing levels of enantioselectivity that hitherto belonged exclusively to the domain of enzymes.…”

mentioning

confidence: 99%

Asymmetric Hydroboration of 1,1‐Disubstituted Alkenes

Thomas

Aggarwal²

2009

Angew Chem Int Ed

129

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“…Sodium boron hydride(NaBH4) was supplied by 1,1972 and -28.6° (lit., 4 [a]n +48.3° and -47.2°). Polyisoprene, polybutadiene, butadiene-styrene copolymer and butadiene-acrylonitrile copolymer (random and alternating 5 ) were purified by precipitation from a benzene solution with methanol.…”

Section: Methodsmentioning

confidence: 99%