Camelia Berghian

Ring-chain tautomerism and other versatile behaviour of 1,4-diimino- and 1,2-phenylene derivatives of some C-substituted serinols

Abstract The behaviour of the title compounds, obtained from terephthaldicarboxaldehyde or 1,2-phthaldicarboxaldehyde and certain (non)chiral C -substituted serinols is discussed in terms of ring (chain)–chain (ring) tautomerism (1,4-phenylene derivatives) or formal intramolecular redox isomerisation (1,2-derivatives).

FIRST SYNTHESIS, ROTAMERISM AND HERBICIDAL EVALUATION OF SUBSTITUTED s-TRIAZINES WITH SERINOLIC FRAGMENT

First example of melamines and precursors, based on commercially C-substituted-2-amino1,3-propanediols (pharmaceutical chemistry nomenclature as serinols) in reaction with cyanuryl chloride is reported, e.g. starting from 2-amino-2-methyl-l,3-propanediol. The diastereomerism generated by the more or less restricted rotation about the C(j -triazine) -N< (serinol) bond in this series is for the first time discussed along with a preliminary herbicidal evaluation of a representative term.

Convenient Synthesis of Chiral 5-Amino-1,3-Dioxanes Built on Some 1-p-Nitrophenylserinols Skeletons

a simple and rapid methodology for the synthesis of the title compounds is described in order to access polvchiral (enantiomerically pure) 5-aminodioxanes in satisfactory yields. The reaction of two nitrophenylserinols with two versatile carbonyl electrophiles (formaldehyde and glyoxal) in very strong acidic conditions (96% H 2 S0 4 ) is discussed together with the limitations of the method. I N T R O D U C T I O N ( l f l ,2 . /? ) -2-Aminol (4-n i t rophenyl ) -propanel ,3-d io l (better known by its trivial n a m e as issued from pharmaceut ical chemist ry as fAreo-p-Nitrophenylserinol) was long t ime cons idered only in connect ion to its N® dich loroace tamido derivat ive, Chloromycet ine . We already reviewed the chemistry of the heterocycl ic saturated systems involved as precursors of p-ni t rophenylser inol and called attention about the ma jo r d i f f e rence be tween the reactivity of the latter and that of phenylserinol itself. On the other hand, only few methods are known to access enant iomerical ly pure 5 -aminol , 3 -d ioxanes by direct r ing closure of the cor responding 2 -aminol , 3 -p ropaned io l s . One of these methods , successfu l ly developed by our group, consisted in the t reatment of the / -p-ni t rophenylser inol (as its 15,25 enan t iomer) with formaldehyde in the presence of an excess of concd. H2SO4 to a f fo rd only the cor responding 2 (45 ,55) -5-amino-4(4-n i t rophenyl ) l ,3 -d ioxane in 7 5 % y i e l d (Scheme I). / 7 N P h = / 7 0 2 N C 6 H 4 Scheme 1 Vol. 7, No. 6, 2001 Convenient synthesis ofchiral 5-amino-l,3-dioxanes built on some 1-p-nitrophenylserinols skeletons In our previous research, the above selective cancellation of nucleophylicity of p-nitrophenylserinol (Scheme 1) allowed us, recently, the complete diastereoselective synthesis of various 1,3-dioxanic Schiff-bases built on its skeleton and. in a more general approach, to describe in terms of ring-chain tautomerism, such type of cyclocondensation. 7 In this paper, it is our intention to enlarge the area of the investigation towards more complex 1,3dioxane structures by direct ring closure of the appropriate p-nitrophenylserinols. Preliminary results are hereafter discussed. R E S U L T S A N D D I S C U S S I O N The chemistry we followed is depicted in Scheme 2 and 3. All synthesis started f rom enantiomerically pure (15,25)-i>-nitrophenylserinol, la. N J J 2 i ) C I C H 2 C O O H / CH-iO / HCOOH I 2 N a 2 C 0 3 / H 2 0 reflux / > N P h reflux J Q N M e 2 l a ii) Η OH OH

FIRST SYNTHESIS, ROTAMERISM AND HERBICIDAL EVALUATION OF SUBSTITUTED s-TRIAZINES WITH AMINO-1,3-DIOXANE GROUPS

First pure enantiomeric 5-amino-l,3-dioxane, obtained by total diastereospecific ring closure of (1 S,25)-2-amino-1 -(4-ni-trophenyl)-1,3-propanediol (nitrophenylserinol) reacted with cyanuryl chloride to afford TV-substituted amino-j-triazines and melamine. Their rotameric behaviour around the C(i -triazine)-N(l,3-dioxane) bond is discussed in terms of NMR, as steric and electronic influence of the substituents. The herbicidal evaluation of one of the new compounds is also described.

FIRST EXAMPLE OF LONG DISTANCE STEREOCONTROLLED SYNTHESIS IN 1-AZA-3,7- DIOXABICYCLO[3.3.0.]OCTANE SERIES

The diastereoselective synthesis of (lÄ*J5*,2S*,2Ä*>55*,5Ä*,8Ä*,85*)-bis-l,4-{l-aza-5-methyl-8-(4-nitrophenyl)-3,7dioxabicyclo[3.3.0]octane-2-yl}benzene is described as the first example of a long distance stereocontrolled synthesis of this type of structure. The thermodynamic control of the reaction together with complete NMR evidence to support the stereochemistry of this compound are discussed. INTRODUCTION The l-aza-3,7-dioxabicyclo[3.3.0]octane heterocyclic saturated system A (Scheme 1) as an easily available analogue of the core alkaloid pyrolizidine Β is known since de pioneering works of Senkus (1,2), Pierce (3, 4) and Bergmann (5). 4 ^ 6 4 6 3 0 5 1 θ 7 3< 1,1 2 φ 8 2 φ 8