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Communication

Synthesis of 1,2,3,6-Tetrahydrophosphinine 1-Oxides by Regioselective Reduction of 1,2-Dihydrophosphinine 1-Oxides

1
Department of Organic Chemical Technology, Technical University of Budapest, 1521 Budapest, Hungary
2
EGIS Pharmaceuticals, 1475 Budapest, Hungary
3
Central Research Institute of Chemistry for Hungarian Academy of Sciences, 1525 Budapest, Hungary
4
Department of General and Analytical Chemistry, Technical University of Budapest, 1521 Budapest, Hungary
*
Author to whom correspondence should be addressed.
Molecules 1997, 2(2), 46-48; https://doi.org/10.3390/feb97p4
Submission received: 20 October 1996 / Accepted: 25 October 1996 / Published: 25 February 1997

Abstract

:
Synthesis of 1,2,3,6-tetrahydrophosphinine 1-oxides by regioselective reduction of 1,2- dihydrophosphinine 1-oxides was reported in this communication.

The formation of unsaturated phosphine-borane complexes from the corresponding phosphines and the dimethylsulfide borane (BMS) reagent may be accom- panied by reductive side-reactions giving rise to saturated derivatives. Thus, the preparation of dihydrophosphinine borane 2 from dihydrophosphinine 1 and the BMS reagent was complicated by the formation of tetrahydro derivative 3 (Scheme 1) [1]. The similar synthesis of phosphepine borane 5 was not only accompanied by the formation of the dihydrophosphepine (6), but also by that of the tetrahydro derivative (7) (Scheme 2) [1]. The product compositions were summarized in the Table.
The reducing ability of the BMS reagent is of wider applicability, as was also suitable for the conversion of the dihydrophosphinine oxides (8) to the corresponding tetrahydro derivatives (9) (Scheme 3).
The reductions were complete after stirring at 24–40°C for 20–30 hr followed by hydrolysis. Starting from the isomeric mixture (A and B) of the dihydrophosphinine (8), the products (9) also consisted of two double-bond isomers (A and B). Isomer B was the mixture of two diastereoisomers. After purification by column chromato- graphy, the isolated yield of the reduced product (9A and 9B) fell in the range of 22-61%.
Scheme 1.
Scheme 1.
Molecules 02 00046 sch001
Scheme 2.
Scheme 2.
Molecules 02 00046 sch002
Scheme 3.
Scheme 3.
Molecules 02 00046 sch003
Table 1. Product compositions of the phosphine-BMS reactions.
Table 1. Product compositions of the phosphine-BMS reactions.
Starting materialProducts (%)
12 (90), 3 (10)
45 (60), 6 (22), 7 (18)
The reduction probably takes place through hydrobo- ration of the α, β-double bond of 8. The intermediate so formed must be very unstable, as we could not determine it by means of spectroscopy.
The selectivity of the reduction was assumed to be due to steric and electronic factors. Detailed results will be reported elsewhere [2].

Acknowledgement 

The authors thank the OTKA support of this work (Grant No. T 014917).

References

  1. Keglevich, Gy.; Újszászy, K.; Szölôssy, Á.; Ludányi, K.; Tôke, L. J Organomet. Chem. 1996, 516, 139.
  2. Keglevich, Gy.; Újszászy, K.; Szölôssy, Á.; Ludányi, K.; Tôke, L. submitted for publication. 1996.
  • Sample Availability: Supporting sample 9Aa, MDPI 4684, is available from MDPI.

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MDPI and ACS Style

Keglevich, G.; Újszászy, K.; Ludányi, K.; Szöllôsy, Á.; Tôke, L. Synthesis of 1,2,3,6-Tetrahydrophosphinine 1-Oxides by Regioselective Reduction of 1,2-Dihydrophosphinine 1-Oxides. Molecules 1997, 2, 46-48. https://doi.org/10.3390/feb97p4

AMA Style

Keglevich G, Újszászy K, Ludányi K, Szöllôsy Á, Tôke L. Synthesis of 1,2,3,6-Tetrahydrophosphinine 1-Oxides by Regioselective Reduction of 1,2-Dihydrophosphinine 1-Oxides. Molecules. 1997; 2(2):46-48. https://doi.org/10.3390/feb97p4

Chicago/Turabian Style

Keglevich, György, Kálmán Újszászy, Krisztina Ludányi, Áron Szöllôsy, and László Tôke. 1997. "Synthesis of 1,2,3,6-Tetrahydrophosphinine 1-Oxides by Regioselective Reduction of 1,2-Dihydrophosphinine 1-Oxides" Molecules 2, no. 2: 46-48. https://doi.org/10.3390/feb97p4

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