A dynamic chemiluminescent process. cyclic and acyclic pathways in the photooxidative decarbonylation of 5-methylfurfural

Tetrahedron Letters,Vol.24,No.ll,pp Printed in Great Britain

oO40-4039/83/111193-04$03.00/O 01983 Pergamon Press Ltd.

1193-1196,1983

CHEMILUMINESCENTPROCESS.

A DYNAMIC

CYCLIC AND ACYCLIC PATHWAYS IN THE PHOTOOXIDATIVE

DECARBONYLATION

OF 5-METHYLFURFURAL

Ben L. Feringa"

and Robert .I. Butselaar

KONINKLIJKEfSHELL-LABORATORILJM, (Shell Research

AMSTERDAM

B.V.), The Netherlands

The pkotooxitlative deccrbm~5nti.nnof 5-m&hyZfurfuraZ was found to prioceed via ar,a-hydroperoxL//hemiacetaZ intermediate or via a cyclic chemiluminescent pathway.

The a-hydroperoxycarbonyl such as dioxygenase

mechanisms 4 and bioluminescence of several a-hydroperoxyketones a predominant

acyclic

carbonyl

here report on the dynamic be mildly pathway,

and selectively

Photooxidation

role in important metabolic

and indole-3-acetic

112 94 95 (luciferin oxygenation). has been studied addition

and a minor

decarbonylation

to proceed

(1) - dissolved

of the photooxidative

conversion

decarbonylation

has been explained

(dark) and a cyclic

intermediate

in dry methanol into methyl is outlined

decomposition

1,2-dioxetane

of 5-methylfurfural,

via an acyclic

of an a-hydroperoxyhemiacetal

in its quantitative

The base-catalysed

cyclic

processes

acid decarboxylation

in detail and the a-cleavage

mechanism

chemiluminescent

of 5-methylfufural

3 h at 40 "C resulted

plays a central

ring cleavage)lm3

directed

and the isolation

The mechanism

structure

(e.g. phenol

a reaction

which

(chemiluminescent)

of the acyclic pathway. containing

rose bengal

for

formate, water and lactone -78. in Scheme

1.

1 to give the bicyclic ozonide 2g-12, in which the found to be completely in the hemiacetal form. The facile is attributed to the influence of the two a-oxy substituents on the aldehyde

At -60 "C singlet oxygen reacted rapidly with aldehyde

moiety was unexpectedly

hemiacetal function selective

formation (comparable methanol

pure form below

to hemiketal

addition

formation

generates

10 'C (oil; mixture

in a-ketoesters7).

At 0 'C a quantitative

the a-hydroperoxyhemiacetal

of two diastereoisomers)12.

1193

by

pathwaylb9697.

compound 3, isolated

stereoin the

We can

1194

To our knowledge proposed

acyclic

accordance tively

compound -3 is the first isolated

decarbonylation

with this mechanism,

into 1, methyl

mechanism

-3 decomposes

formate and water

and characterized

of cr-hydroperoxycarbonyl at more elevated

intermediate

compounds1bp6y7.

temperatures

(> 20 "C) quantita-

1, path a) with first-order

(Scheme

of the In

kinetics

(k, =

1.34 x lop4 s-l at 40 "C). Surprisingly,

when methanol

O-5 "C and the residue

and the concentration

-4 decomposed

quantitatively

was constant

during

an enhanced

formation

decarbonylation (not detected

intermediate),

was measured

during

depended

was increased

to an intermediate

followed by a fast cleavage

as we confirmed

of the equilibrium the decomposition

independently.

the formation

mixture

above

15 'C,

for-mate to formic acid

hydroxydioxetane

to 1 (Scheme

to decomposition In conformity

of chemiexcitated

however,

increase.

The

-6

1, path b).

of the hydrate 2 with the decomposition

lactone 1 during

the

of 2 and 4 in CHC13 at 22 'C. The chemiluminescence

of -4 in the presence

(DPA) and 9,10-dibromoanthracene

4

upon solvent,

the period of temperature

of -7 and formic acid cannot be attributed conditions

of -3 at

of -3 and -4 at a given temperature;

during

via cyclization

solution

the a-hydroperoxyaldehyde

(Scheme 1) strongly

of the mixture

of formic acid is observed

of -4 via the hydroxydioxetane6 - we observed slow decomposition

from the methanolic

When the temperature

of methanol.

the decomposition

as a stable

the reaction

anthracene

removed

in dry chloroform,

into -7 and formic acid. The ratio of methyl

of -4 can be explained

The formation under

dissolved

(3/4 _- N 7/3 at 22 "C). The equilibrium

was formed" temperature

was carefully

subsequently

(DBA).

of added fluorescers

9,10-diphenyl-

1195

FIGURE

DPA fluorescence formic acid

(Icl) decay curve

(FA) concentration

sition of -3+4

1

(0) and methyl

vs time (- -

in CDC13 at 50 "C (3+4, -

l

formate

(MF),

- -) for decompo-

6.15 x 10s2 M; DPA,

2.0 x 1O-2 M) Figure

1 shows the time-dependent

of -4 as detected by NMR during decomposition in CHC13. In methanol as the solvent, where no -4 was present, chemiluminescence in the presence of fluorescers DPA or DBA, was essentially zero. Addition of methanol

to the chloroform

decomposition

upon heating.

DPA fluorescence

solution

This means

(neutral medium,

room temperature)

chemiluminescent

pathway,

and the conversion

of -3 and -4 also resulted that the oxidative

dynamic

solely depends

system in which

in a non-chemiluminescent

decarbonylation the selection

on, and can be directed

represents

a very mi Id

of a dark or a

by, the hemiacetalization

equilibrium. As the preparation to completely furfural

suppress

derivative

with previous

of 2 and -4 requires

the use of a hydroxylic

the dark decomposition

E12r13,

observationstO,

which

contains

8 yielded

solvent,

(path a). Such a pathway

an internal hydroxyl

group

the Spiro-a-hydroperoxyaldehyde

it was not possib le

is avoided with the (Scheme 2). In agreement -912, which decomposed

-14. into lactone -11 and formic acid SCHEME 2

I

-H3cs0

+

H!OH

+

hv

1196

DPA- and DBA-enhanced with a hydroxydioxetane

chemiluminescence

was observed

10, thus confirming

intermediate

pathway

(path b) for 2. Mild ways of chemiexcitation

deserve

consideration

in the elucidation

in several pathological

during decomposition a predominantly

of 2 in agreement

cyclic

such as the one reported

of in vivo mechanisms

decomposition

in this paper

of chemiexcitation2s4

resulting

effects.

Acknowledgement I"ileauthors wish to thank Mr. J.H.C. Frijns for his contributions to the NMR studies;

Professor H. Wynberg for the use of the chemiluminescencedetection faciZities of the University of Groningen and Dr. E.W. Meyer and Dr. J.C. Humelen for recording the spectra. REFERENCES in: "Molecular Mechanisms of Oxygen Activation"; 0. Hayaishi, ed., Academic Press, New York, 1974, p. 405; W.H. Richardson, V.F. Hodge, D.L. Stiggall, M.B. Yelvington and F.C. Montgomery, J. Am. Chem. Sot., 1974, 96, 6652.

1 .a) G.A. Hamilton

b) 2.

E.H. White, J.D. Miano, 1974, 2, 229.

3.

I. Saito, T. Matsuura in: "Singlet Oxygen", Academic Press, New York, 1979, p. 511.

4.

G. Cilento,

5.

E.H. White, M.G. Steinmetz, J.D. Miano, 1980, 102, 3199; and references cited.

P.D. Wildes

6.

Y. Sowaki, Y. Ogata, J. Am. Chem. Sot.,

1977, 2,

7.

C.W. Jefford,

8.

No other

C.J. Watkins

Act. Chem. Res.,

and E.J. Breaux, Angew.

1980, 2,

H.H. Wasserman

Chem.,

Internat.

and R.W. Murray,

Edit.,

ed.,

225. and R. Morland,

J. Am. Chem. Sot.,

5412.

W. Knljpfel and P.A. Cadby, J. Am. Chem. Sot., 1978, 100,

6432.

products were observed in the NMR spectra.Lactone 1. isolated by distillation in 90 % yield (bp 40-42 'C, 0.05 mm Hg), was prepared independently from 2-methylfuran 9310.

9.a) C.S. Foote, M.T. Wuesthoff, S. Wexler, I.G. Burstain, K.H. Schulte-Elte, Tetrahedron, 1967, 23, 2583; Oxygen", b) H.H. Wasserman, B.H. Lipschutz, in: "Sxglet Academic Press, New York, 1979, p. 430.

H.H. Wasserman,

and

R.W. Murray,

1981, 1447; B.L. Feringa

eds.,

and

10.

B.L. Feringa and R.J. Butselaar, Tetrahedron R.J. Butselaar, ibid., 1982, 1941.

11.

B.L. Feringa, Tetrahedron 1980, 102, 404.

12.

All new compounds showed spectral and physical data consistent with the Some representative NMR data are: 2 'H NMR (CDC13)6 2.02 (s, 3H), 4.95, 5.32 (br.s, lH), 6.55, 6.75 (2 ABsystems, J = 5,8 Hz, J = 6.0 Hz, 2H); 12.0, 92.2, 112.0, 112.2, 112.5, 130.7, 131.0, 133.3; 3 1H NMR (CD OD)6 3.31 (br.s, 3H), 3.45, 3.49 (2s, 3H), 4.75 (br.s, 2H),-4.97, 5.05 ?2 s, (2 AB systems, J = 6.0 Hz, 2H); '3C NMR (CD OD) 23.9, 94.8, 95.6, 112.6, 126.2, 135.6, 136.3; 4 1~ NMR (CDCl )6 l.583(s, 3H), 3.23 (s, 3H), 5.35 6.30 (AB system, J = 5.5 HZ, 2H), 9166 (s, IH).

structures indicated. 4.99 (2s, 1H) 13C NMR (CD OD)6 1.51 1.54 ?2s, 3H), lH),'6.08, 6.10 114.2, 114.4, 126.0, (br.s, IH) 5.93,

13.

Furfural derivative 5 is conveniently butanol-2 followed by acid hydrolysis

of 4-(2-furyl)-

14.

The selectivity towards 9 was 80 % at 65 % conversion of probably the results of radical reactions in CHC13, were remained unchanged during the quantitative conversion of

(Received

in

UK

23

Lett.,

November

Lett.,

R. Denny, G.O. Schenck

1981, 1443; W. Adam and A. Rodriquez,

prepared by Vilsmeyer formylation of the formic acid ester of _8.

1982)

J. Am. Chem. Sot.,

8; unidentified by-products, observed. These products, however 9 to -Il. -