Synthesis of <i>N,O</i>-Type Inherently Chiral Calix[4]arenes Substituted on the Lower Rim and their Organocatalysis Properties

Chang, Ming-Liang; He, Yong; Zhou, Jing; Li, Shao-Yong

doi:10.21577/0103-5053.20160307

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Articles • J. Braz. Chem. Soc. 28 (08) • Aug 2017 • https://doi.org/10.21577/0103-5053.20160307 linkcopy

Synthesis of N,O-Type Inherently Chiral Calix[4]arenes Substituted on the Lower Rim and their Organocatalysis Properties

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

This work presented the first study of organocatalytic behaviors of inherently chiral calix[4]arenes substituted at the lower rim. A pair of N, O-type enantiomers based on inherently chiral calix[4]arenes substituted at the lower rim were readily synthesized and applied to catalyze Henry reaction between aromatic aldehydes and nitromethane. Their organocatalytic reaction can afford the desired products in excellent yields (up to 99%) but poor enantioselectivities (up to 7.5% ee).

Keywords:
inherently chiral; calix[4]arene; asymmetric catalysis; Henry reaction


entrya	Catalyst	Solvent	Temperature / ºC	time / h	Configuration	Yieldd / %	eee / %
1	5a	CH₃CN/H₂Ob	rt	6	S	94	7.3
2	5b	CH₃CN/H₂Ob	rt	6	S	93	5.4
3	5a	THF/H₂Ob	rt	6	S	99	1.2
4	5b	THF/H₂Ob	rt	6	R	99	4.0
5	5b	CH₃CNc	rt	48	-	-	-
6	5b	THF	rt	48	R	30	1.6
7	5a	EtOH/H₂Ob	rt	6	S	54	7.5
8	5b	EtOH/H₂Ob	rt	6	R	63	1.1
9	5a	EtOH	rt	6	S	60	2.3
10	5b	EtOH	rt	6	-	65	0
11	5a	EtOH/H₂Ob	-10	24	S	84	0.1
12	5b	EtOH/H₂Ob	-10	24	S	89	1.2
13	5a	EtOH/H₂Ob	-25	72	-	60	0
14	5b	EtOH/H₂Ob	-25	72	-	61	0


entrya	R	time / h	Configuration	Yieldc / %	eed / %
1	4-CN	36	S	98	2.1
2	4-F	36	S	85	0.2
3	2-NO₂	12	S	87	1.3
4	3-NO₂	16	S	83	1.2
5	3-Cl	24	S	80	2.7
6	4-MeO	48	S	25	1.0
7	4-N(CH₃)₂b	48	-	-	-
8	2-CH₃	48	S	68	0.5

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[TFN1] ^a
The reaction was performed with 0.6 mmol 4-nitrobenzaldehyde and 6 mmol nitromethane in 4 mL solvent;

[TFN2] ^b
the volume ratio of the former to the latter is 3:1;

[TFN3] ^c
no desired product;

[TFN4] ^d
isolated yield;

[TFN5] ^e
enantiomeric excess was determined by HPLC using a Chiracel OD-H column. The absolute configurations of all products were determined by comparing the retention time from HPLC data on the products with those in the literature data.¹⁹^-²¹