Ruthenium catalyzed oxidation of cyanohydrins to acyl cyanides useful reagents for selective N-benzoylation of aminoalcohols

0040-4039/85 $3.00 + -00 81985 Pergamon Press Ltd.

Tetrahedron Letters,Vol.26,No.7,pp 925-928,1985 Printed in Great Britain

RUTHENIUM USEFUL

CATALYZED

REAGENTS

Shun-Ichi Department

OXIDATION

Murahashi*,

of Chemistry,

Ruthenium

catalyzed

are useful reagents

of cyanohydrins

the hydrogen

is trapped

for a suitable excellent alcohols

oxidant

oxidant

with an appropriate

for the ruthenium

with t-BuOOH

catalyzed

in the presence

under argon gives aldehydes also found the similar

gives acyl cyanides

the ruthenium efficient

catalyzed 4

efficiently

synthesis

During

acceptor.

oxidation

In this paper, we wish to report that ruthenium t-BuOOH

of alcohols

The reaction

of alcohols.

hydroperoxide

is an

of

in benzene at room temperature

of alcohols

Watanabe

et al. have

with t-BuOOH.'

oxidation

under mild conditions.

of a-keto acid derivatives

fast when

the course of searching

The oxidation

yields.

catalyzed

and diols gives

proceeds

we have found that tert-butyl

oxidation

gives the

thus obtained

of aminoalcohols.

in good to excellent

catalyzed

hydroperoxide

Acyl cyanides

of 5 mol% of RuClB(PPhB)S

and ketones

ruthenium

yields.

dehydrogenation

hydrogen

Osaka University,

560, Japan

highly efficiently.'

to trap the hydrogen,

Nakajima

with tert-butyl

N-benzoylation

catalyzed

esters and lactones

Science,

Osaka,

in good to excellent

We have found that the ruthenium the corresponding

Toyonaka,

for selective

TO ACYL CYANIDES OF AMINOALCOHOLS

Naota, and Nobuyuki

Faculty of Engineering

oxidation

acyl cyanides

N-EENZOYLATION

Takeshi

Machikaneyama,

corresponding

OF CYANOHYDRINS

FOR SELECTIVE

Recent

prompted

of cyanohydrins

with

paper3 which reports us to report our

method.

OH

RuC12(PPh3)

0

3

R-LHCN

P t-BuOOH,

R-i&4

benzene

Acyl cyanides are versatile synthetic intermediates and have been utilized in a variety 5 of transformation of CO and CN functions, nucleophilic reaction with enolates,6 and Michael 7 addition. Generally, acyl cyanides have been prepared by the reactions of acid halides with 538 and trimethylsilyl cyanide. 6,9 Alternative method i's the a variety of metal cyanides oxidation

of cyanohydrins

former method acyl cyanides

is advantageous

for the conversion 10 are not isolated.

Acyl cyanides cyanohydrins,

with active manganese

can be conveniently

which are readily

(CH3)3SiCN/Zn12-HC1.

I3

Table

prepared

prepared

dioxide

or pyridinium

of sensitive

dichromate. I1 into esters,

catalyzed

of aldehydes

the representative

925

aldehydes

by the RuC12(PPh3)3

upon treatment

1 summarizes

10

results

The

although

oxidation

with NaHS03-KCNI' of the synthesis

of or of acyl

926

Aromatic

cyanides. cyanides, because

the present

acyl cyanides

method

is advantageous

gave unsatisfactory

Table

1.

over the previous

acids

of conjugated 10 because versatile methods,

gave lower yields

(92%) > CH2C12

of Cyanohydrins Synthetic

Acyl Cyanideb)

of

of benzoyl

(86% and 31%), and RhC1(PPh3)3 is important.

Benzene,

CH2C12,

(81%) > CC14 (80%) > THF (35%) > pyridine

IS . the best oxidant among the oxidants examined.

in dry benzeneI

Conversions

for the oxidation

for the formation

The solvent effect

results.

benzene

has been examined

is the best catalyst

and RuH2(PPh3)4

t-BuOOH

into acyl

carboxylic

For the conversion

of various metal complexes

and CC14 are good solvents; (23%) ' DMF (0%).

efficiently

into the corresponding

acyl cyanides.

RuC12(PPh3)3

RuC13*nH20

are converted

are converted

isolated.

activity

cyanohydrin.

(92%).

and Pd(OAc)2

of unstable

can be easily

The catalytic benzaldehyde

cyanohydrins

cyanohydrins

of the hydrolysis

aldehydes,

cyanide

and a$-unsaturated

while aliphatic

to Acyl Cyanides

a)

Method

of Cvanohvdrinc)

Isolated Time(h)

Yield(%)

3

87

3

99

3

77

11

82

A

2

89

B

15

87

B

24

65

0 :CN 7

0

3 CN CY

92

0

P-+&N

81

a)All

reactions were carried out following the standard procedure described in the text. b)All products showed satisfactory IR, NMR, and Mass spectral data. c) Cyanohydrins were prepared

in 90-95% yields

Zn12-2N.HCl.

according

to the following

methods.

A; NaHS03-KCN,

B; Me3SiCN/

927

Hydrogen

peroxide,

m-chloroperbenzoic

gave unsatisfactory and hence t-BuOOH Typical

should be added slowly

procedure

benzaldehyde benzene

for the oxidation

cyanohydrin

over 20 min.

excess t-BuOOH.

Filtration,

(florisil,

dry ether)

Smooth formation advantageous

Similar

After removal

gave benzoyl of carboxylic

catalyzed

oxidation

in the presence treatment

of t-BuOOH stirring

for 3 hr palladium

(4.0 mmol,

of sensitive

afforded

found that b;:zoyl

cyanides

(1) followed

the corresponding

of 3-amino-1-propanol benzoyl

cyanide

Table 2.

Et3N

Entry

with

G -0Me

/

t-BuOOH b

2

V

NHBu 2

examples

(0.377 g, 5.0 mmol)

N-Benzovlation

Aminoalcohol

by treatment

ester 2 in 85% yield.

2

are highly useful reagents

(0.659 g, 5.0 mmol)

Selective

Typically,

of an amino group in the preseice of a hydroxy group is of 15 amino sugars, and related compounds. We have of alkaloids,

The representative

amino group.

is particularly

gave the amide 3 in 77% yield.

1)RuC12(PPh3)3

N-protection

are listed

in CH2Cl2

in CH2C12

for the selective in Table 2.

benzoylation

Typically,

(15 mL) was added dropwise

(4 mL) at -10°C.

After removal

of an

to a solution a solution

of

of the solvent

of Aminoalcohols a) Productb)

o-ii

Isolated Yield

(%)

n

1

HN-OH 2

2

H,mOH

93

3

H2NWOH

91

4

a)All

at

to decompose

into acid derivatives.

of 2-hydroxy-3-heptenenitrile

Z)MeOH,

in the synthesis

in dry

1.2 mL) dropwise

black was added

from acyl cyanides

aldehydes

2) BuNH2

Selective

of

and short column chromatography

acid derivatives

1

importance

slowly,

(0.228 g, 87%).

c

_CN

To a mixture

(0.096 g, 0.1 mmol)

1)RuC12(PPh3)3/t-BuOOH

QH

and oxygen

proceeds

the oxidation.

is as follows.

in dry benzene

of the solvent,

of triethylamine

with butylamine

sodium periodate, cyanohydrins

(5-6 hr) to complete of cyanohydrins

cyanide

for the transformation

the ruthenium

peroxide,

of a,&unsaturated

(0.266 g, 2.0 mmol) and RuC12(PPh3)3

(4.0 mL) was added a solution

room temperature

methanol

acid, benzoyl

The oxidation

results.

I,\

CNH -OH

92

99

reactions were carried out following the standard procedure described b) All products showed satisfactory IR, NMR, and Mass spectral data.

in the text.

928

the residue was subjected trapped with a sodium with a mixture Benzoyl

chromatography

solution

of ether and methanol

cyanides

on the extention natural

to column

hydroxide

The hydrogen

cyanide

reagents.

generated

(NaClO).

(4:l) gave N-(3-hydroxypropyl)benzamide

are clean and mild acylating

of this reaction

(SiO2).

and then treated with antiformin

was

Elution

(0.830 g, 92%).

Further work is now in progress

to the other system and application

to the synthesis

of

products.

References

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and Notes

Murahashi,

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