Heteroatom Chemistry Volume 18, Number 7, 2007 Reaction of Diethyl Thiocyanatomethylphosphonate with Aldehydes as a Route to Diethyl Z -1-Alkenylphosphonates Roman B laszczyk and Tadeusz Gajda Institute of Organic Chemistry, Department of Chemistry, Technical University of Lodz, Zeromskiego St. 116, 90-924 Lodz, Poland Received 18 September 2006; revised 3 December 2006 ABSTRACT: Diastereoselective synthesis of diethyl Z-1-alkenylphosphonates from easily available diethyl thiocyanatomethylphosphonate and aromatic aldehy- des has been developed. Olefination of the aldehydes occurs under mild conditions and affords the title compounds with moderate yields. A plausible mech- anism of the above-mentioned reaction is also dis- cussed. C  2007 Wiley Periodicals, Inc. Heteroatom Chem 18:732–739, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20371 INTRODUCTION Organic thiocyanates are valuable tools for the synthesis of a wide variety of organosulfur com- pounds [1]. Increasing interest in the chem- istry of bifunctional organic compounds contain- ing both phosphorus and sulfur moieties resulted in the efficient synthesis of racemic [2] as well as optically active 1-(thiocyanato)alkylphosphonates [3], their application in the preparation of the α-sulfanylphosphonates [3], potential metalloen- zyme inhibitors. Being inspired by the work of Hayashi et al. [4] who found the condensation of thio- Correspondence to: Tadeusz Gajda; e-mail: tmgajda@p.lodz.pl. c  2007 Wiley Periodicals, Inc. cyanatoacetic acid esters with aromatic aldehy- des as a route to 2-imino-1,3-oxathiolanes, we fo- cused our attention on the reactions of diethyl thiocyanatomethylphosphonate 1 with aldehydes 2, which could lead to new derivatives of 2- imino-[1,3]-oxathiolan-4-yl)phosphonates 3 and/or 2-hydroxy-1-mercaptophosphonates 4 (Scheme 1). However, the above-mentioned reactions afforded α,β-unsaturated phosphonates instead of the desired products 3 and 4. This observation prompted us to direct our investigations toward the synthesis of alkenylphosphonates. Alkenylphosphonates are important intermedi- ates in organic chemistry [5], especially for the synthesis of carbo- and heterocyclic compounds [5a,6] as well as various functionalized phospho- nates [5a,7]. Although a number of methodologies have been developed for the synthesis of E-1- alkenylphosphonates [8], there is still a place for the new protocols directed to the preparation of Z- alkenylphosphonates [5a]. So far, these compounds are available by Horner–Wadsworth–Emmons (HWE) olefination of aldehydes with tetrakis(2,2,2- trifluoroethyl)methylenebisphosphonate [9], palla- dium-catalyzed coupling of dialkyl phosphites with Z-1-bromo-1-alkenes [10], and copper-promoted substitution of vinyl bromides with dialkyl and diphenyl phosphites in the presence of base [11]. Other convenient methodologies are 732